help button home button Endocrine Society Endocrinology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology, doi:10.1210/en.2005-1431
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
147/7/3472    most recent
Author Manuscript (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Grapengiesser, E.
Right arrow Articles by Hellman, B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Grapengiesser, E.
Right arrow Articles by Hellman, B.
Endocrinology Vol. 147, No. 7 3472-3477
Copyright © 2006 by The Endocrine Society

Glucose Induces Glucagon Release Pulses Antisynchronous with Insulin and Sensitive to Purinoceptor Inhibition

Eva Grapengiesser, Albert Salehi, Saleem S. Qader and Bo Hellman

Department of Medical Cell Biology (E.G., B.H.), University of Uppsala, SE-75123 Uppsala, Sweden; and Departments of Experimental Medical Science (A.S.), and Surgery (S.S.Q.), University of Lund, SE-22184 Lund, Sweden

Address all correspondence and requests for reprints to: Professor Bo Hellman, Department of Medical Cell Biology, Biomedicum Box 571, SE-75123 Uppsala, Sweden. E-mail: Bo.Hellman{at}medcellbiol.uu.se.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Both increase of the glucose concentration and activation of purinoceptors are known to affect pancreatic {alpha}-cells. Effects obtained with various purino derivatives at 2.8 and 8.3 mmol/liter glucose have been taken to indicate that external ATP is less potent than adenosine as a stimulator of glucagon release. However, when making a corresponding comparison at 20 mmol/liter glucose, we observed marked stimulation of glucagon release from isolated rat islets with 100 µmol/liter adenosine-5-O-2-thiodiphosphate but inhibition with 10 µmol/liter adenosine. Analyses of 30-sec samples of perfusate from rat pancreas indicated that a rise of the glucose concentration from 3 to 20 mmol/liter rapidly induces a glucagon peak followed by regular 4- to 5-min pulses. The glucagon pulses preceded those of insulin with a phase shift (1.8 ± 0.1 min) near half the interpeak interval. Because of the antisynchrony, the maximal glucagon effect on liver cells will be manifested during periods with low concentrations of insulin. In support for the idea that neural P2Y1 receptors are important for coordinating the secretory activity of the islets, both the insulin and glucagon pulses disappeared in the presence of the purinoceptor inhibitor MRS 2179 (10 µmol/liter). However, in contrast to what was observed for insulin, MRS 2179 lowered average glucagon release to the level of the oscillatory nadirs.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
THE CYCLIC VARIATIONS of circulating islet hormones reflect pulsatile release into the portal vein (1, 2). Both the insulin-producing ß-cells (3) and the cells producing glucagon (4, 5), somatostatin (4, 6), and pancreatic polypeptide (7) have an intrinsic ability to generate oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i). In the isolated cells, these oscillations vary considerably with regard to duration and frequency. A prerequisite for pulsatile release of a hormone into the portal vein is that the secretory [Ca2+]i signal is entrained into a common rhythm. Within the islets, synchronization is mediated via both gap junctions (8) and diffusible messengers, such as NO (9) and ATP (10). Accordingly, it is possible to demonstrate pulsatile release of insulin from isolated islets, the frequency of which is fairly constant irrespective of the islet size (11). Neural activity with discharge of ATP is supposed to affect the membrane potential in a way causing the ß-cells from different islets to appear in the same oscillatory phase (12).

Glucose is a stimulator of insulin secretion but usually suppresses release of glucagon from the {alpha}-cells. Together with insulin, the level of glucagon determines the rate of gluconeogenesis and glycogenolysis in the liver. Accordingly, glucagon has a key role for the counterregulatory response to hypoglycemia (13). The ability of glucose to suppress glucagon secretion has been attributed both to a direct action on the {alpha}-cells (13, 14, 15, 16, 17) and to paracrine effects mediated by adjacent cells (6, 13, 17, 18, 19). The {alpha}-cells may also have effects on the ß-cells, because glucagon promotes the generation of [Ca2+]i transients supposed to synchronize the slow [Ca2+]i oscillations (20).

We recently observed that the purinoceptor inhibitor MRS 2179 removes the pulsatility of insulin released from the perfused rat pancreas with maintained synchronization of the [Ca2+]i oscillations in aggregates of ß-cells (21). Taking advantage of the same protocol for pancreas perfusion, it is now shown that pulses of glucagon are related to insulin in a fashion providing maximal exposure of liver cells to glucagon during periods of low concentrations of insulin. Like the insulin release pulses, those of glucagon were removed by MRS 2179, suggesting that neural P2Y1 receptors are important for coordinating the secretory activity of the islets.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals
Female Sprague Dawley rats, weighing 250–300 g, were used. The animals were allowed free access to food. Before perfusion of pancreas, the rats were anesthetized with 5% chloral hydrate (1 ml/100 g body weight). The experiments were approved by a local ethical committee.

Chemicals and solutions
Reagents of analytical grade and deionized water were used. Roche Diagnostics (Mannheim, Germany) supplied adenosine deaminase and collagenase. The P2Y1 receptor antagonist 2-deoxy-N-methyladenosine 3,5-bisphosphate (MRS 2179) was a product of Tocris Cookson (Bristol, UK). ATP (ultragrade), adenosine, and adenosine-5-O-2-thiodiphosphate (ADP-ß-S) were obtained from Sigma Chemical Co. (St Louis, MO). Trasylol (aprotinin) was bought from INC Pharmaceuticals (Aurora, OH). The studies were performed at 37 C with a basal medium of Krebs Ringer bicarbonate buffer, supplemented with 10 mmol/liter HEPES, and gassed with 5% CO2 and 95% O2 to pH 7.4. Concentrations of hormones in the perfusate were measured in duplicate with RIA. In the case of glucagon, degradation was prevented with aprotinin (80 mg/liter), and the ethanol precipitation step in the assay was replaced by charcoal separation (22). The antiserum used for determination of glucagon (Milab Ltd., Malmö, Sweden) was highly selective for pancreatic glucagon.

Perfusion of pancreas
Perfusion of pancreas was performed with a protocol that allows contribution of blood from the donor (21). Unrecycled medium, supplemented with 2% BSA (wt/vol), was infused at a rate of 0.4 ml/min. After 5 min of equilibration, effluent from the portal vein was collected as 30-sec portions in heparinized vials, centrifuged, and stored at –20 C. The contribution of blood to the perfusion medium was 25%, as estimated from a comparison of the glucose concentration in the effluent with that in the circulating blood.

Release from isolated islets
Islets were isolated with collagenase (23) and preincubated for 30 min in basal medium supplemented with 0.1% BSA and 3 mmol/liter glucose. Each vial contained 25 islets in 1.0 ml medium. After preincubation, the medium was replaced and the islets were exposed to test substances during 45 min in the presence of 20 mmol/liter glucose.

Analysis of data
Statistically significant hormone pulses were identified with the cluster analysis program, a computerized pulse analysis algorithm (24). Each sample was assigned a dose-dependent SD, calculated from the actual duplicates within the experiment. A sliding pooled t test was then performed to identify data points within the time series that correspond to statistically significant increases and decreases of the hormone concentrations. Test cluster sizes for the nadir and the peak widths were assigned to 2 (2 x 2). The minimum t statistic was specified to 4.1 for upstrokes and downstrokes, respectively. These settings detected peaks with less than 1% false positive errors. The concentration time series after the initial glucagon peak was lagged relative to the time series of insulin. The cross-correlation analysis was performed using the International Mathematics and Statistics Library routine DCCF (25).

Results are presented as mean values ± SEM. Differences were statistically evaluated with t test.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Glucose induction of glucagon pulses
Increase of the glucose concentration from 3 to 20 mmol/liter resulted in repeated pulses of glucagon release with nadirs below those seen at the low glucose concentration (Fig. 1Go). In a majority of the rats (14 of 15), there was a distinct initial peak starting within 30 sec (Fig. 2Go). Although inducing sustained glucagon rhythmicity, the rise of the glucose concentration to 20 mmol/liter left average secretion essentially unaffected. In the five experiments shown in Fig. 1Go, the concentration of glucagon before the increase of glucose was 242 ± 58 ng/liter compared with 206 ± 13 ng/liter during the period of sustained glucagon rhythmicity (P > 0.05).


Figure 1
View larger version (20K):
[in this window]
[in a new window]
  		FIG. 1. Pulses of glucagon release generated by increase of the glucose concentration from 3 to 20 mmol/liter during perfusion of rat pancreases 1–5. Perfusate from the portal vein was collected as 30-sec portions and duplicate samples taken for analyses. The vertical bars represent internal SD calculated from the assay duplicates within the experiment. Statistical evaluation, using the cluster analysis program, indicated sustained glucagon rhythmicity at 20 mmol/liter glucose in all 15 experiments. In rat 5, the unusually high glucagon level before raising the glucose concentration probably explains the absence of an initial peak. *, Statistically verified pulses (P < 0.01). Each mark on the ordinate indicates 0 ng/liter glucagon for the trace above and/or the 500 ng/liter level for the trace below.

 

Figure 2
View larger version (14K):
[in this window]
[in a new window]
  		FIG. 2. Characterization of the initial glucagon peak induced by raising glucose from 3 to 20 mmol/liter during perfusion of rat pancreas. Perfusate from the portal vein was collected as 30-sec portions. The glucagon concentration before raising glucose was higher (155 ± 15 ng/liter) than the nadir (76 ± 7 ng/liter) after the peak (P < 0.001). Results shown are mean values ± SEM for 14 experiments.

 
Temporal relation between glucagon and insulin rhythmicity
The glucagon rhythmicity was clearly related to that of insulin (Fig. 3Go). Comparing the contents of the hormones within each 30-sec sample, it was found that the initial glucagon peak preceded that of insulin. During the subsequent period of sustained rhythmicity, the glucagon pulses were antisynchronous with those of insulin (Figs. 3Go and 4Go). The pulse period of glucagon (4.4 ± 0.2 min) was similar to that of insulin. Cross-correlation analyses indicated a phase shift (1.8 ± 0.1 min; n = 5) near half the interpeak interval. Consequently, the periods of glucagon increase coincided with lowering of insulin, and vice versa.


Figure 3
View larger version (19K):
[in this window]
[in a new window]
  		FIG. 3. Glucose-induced pulses of glucagon and insulin release in rat 2 from Fig. 1Go. Both glucagon and insulin started to increase when the glucose concentration was raised from 3 to 20 mmol/liter. The initial glucagon pulse preceded the corresponding insulin pulse. During the subsequent period of sustained rhythmicity, the pulse order was maintained, so that the rise of glucagon was related to a decrease of insulin and lowering of glucagon to an increase of insulin.

 

Figure 4
View larger version (13K):
[in this window]
[in a new window]
  		FIG. 4. Cross-correlation analyses of the relationship between glucagon and insulin pulses in rats 1–5 from Fig. 1Go during the period of sustained rhythmicity. The glucagon pulses were phase-shifted with 1.8 ± 0.1 min (P < 0.001).

 
Effects of modulators of purinoceptor signaling
The effects of 10 µmol/liter MRS 2179 on the sustained rhythmicity of glucagon and insulin are shown in Fig. 5Go. The addition of this P2Y1 inhibitor rapidly removed the pulsatility of both hormones. The oscillations tended to reappear after removal of MRS 2179. Comparing the highest and lowest hormone concentrations during 2-min periods before and after 5 min omission of MRS 2179, the difference increased with 61 ± 11 ng/liter (P < 0.01) for glucagon and 185 ± 15 pmol/liter (P < 0.001) for insulin. Contrary to the increase of average insulin secretion seen in the presence of MRS 2179, there was no corresponding rise of glucagon but a lowering to the level of the oscillatory nadirs.


Figure 5
View larger version (21K):
[in this window]
[in a new window]
  		FIG. 5. Suppressive action of MRS 2179 (10 µmol/liter) on glucagon and insulin pulses induced by 20 mmol/liter glucose. Perfusate from the portal vein was collected as 30-sec portions and duplicate samples taken for analyses. The vertical bars represent internal SD calculated from the assay duplicates within the experiment. *, Pulses statistically verified by cluster analysis (P < 0.01). Five minutes after omission of MRS 2179, the pulses tended to reappear. Results are representative of five experiments.

 
Additional evidence that MRS 2179 suppresses the release of glucagon at 20 mmol/liter glucose was obtained in experiments with isolated islets. During 45 min of incubation, MRS 2179 inhibited glucagon secretion (Fig. 6AGo) but stimulated the release of insulin (Fig. 6BGo). Another experiment (not shown) indicated that 10 µmol/liter adenosine was a stimulator of glucagon release in the presence of 8.3 mmol/liter glucose (10.1 ± 1.1 vs. 22.5 ± 1.7 pmol/islet; P < 0.001) but was inhibitory at 20 mmol/liter glucose (Fig. 6CGo). Testing other modulators of purinoceptor signaling at 20 mmol/liter glucose, it was found that 100 µmol/liter ATP, 100 µmol/liter ADP-ß-S, and 1 U/ml adenosine deaminase stimulated glucagon release (Fig. 6CGo). MRS 2179 counteracted the release of glucagon also when the {alpha}-cells were exposed to adenosine deaminase (P < 0.01).


Figure 6
View larger version (23K):
[in this window]
[in a new window]
  		FIG. 6. Effects of modulators of purinoceptor signaling on the release of glucagon (A and C) and insulin (B and D) from isolated rat islets exposed to 20 mmol/liter glucose. The bars denote the amounts of hormone released per islet during a 45-min incubation. Additives to the media were MRS 2179 (MRS), 100 µmol/liter ATP, 100 µmol/liter ADP-ß-S, 10 µmol/liter adenosine (Ad), and 1 U/ml adenosine deaminase (Ad-deam). Results shown are mean values ± SEM for 10–12 experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001 compared with medium lacking additive.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
This study shows that a rise of the glucose concentration from 3 to 20 mmol/liter during perfusion of rat pancreas rapidly induces a glucagon peak followed by regular 4- to 5-min pulses. The pulsatile release of glucagon occurred without significant changes of the average secretory rate. The rhythmicity resembled that seen when insulin release is stimulated under identical conditions (21). In ß-cells the glucose-induced increase of cytoplasmic ATP is supposed to close KATP channels, resulting in rhythmic depolarization with periodic entry of Ca2+. Several authors have reported functionally active KATP channels also in {alpha}-cells (15, 18, 26, 27). Both the glucose induction of an introductory glucagon peak and the subsequent pulsatility may result from inhibition of these channels.

Analyses of the temporal relationship between the pulses of glucagon and insulin are critically dependent on the methodology employed. Because insulin and glucagon have relatively short pulses (4 to 5 min), most of the early studies do not meet the requirements of a sufficient sampling frequency (2). Whereas some authors have failed to demonstrate a consistent relationship between the glucagon and insulin cycles (28, 29), others have observed that the pulses are generated simultaneously (30) or with a phase difference (31, 32). Measuring the contents of the two hormones in 30-sec samples of perfusate, we now conclude that the pulses of glucagon release are antisynchronous with those of insulin with a phase difference of about 2 min. Interestingly, Lang et al. (32) observed a similar phase difference in plasma from human subjects using a technique reporting the periods of glucagon and insulin to be 13–14 min.

Isolated {alpha}-cells generate spontaneous [Ca2+]i oscillations with a frequency of 0.1–0.3/min (5). When entrained into a common rhythm within and among the islets, the oscillations of [Ca2+]i trigger pulsatile release of glucagon into the portal vein. The observation of a time difference between the glucagon and insulin pulses as long as 2 min is difficult to reconcile with early reports of gap junctions between {alpha}- and ß-cells (33, 34). However, after improvement of the technique for identification of cells in intact islets it was concluded that the electrical coupling between the {alpha}- and ß-cells is weak or absent (15). So far, attempts to demonstrate synchronization of the [Ca2+]i oscillations in {alpha}-cells situated within the same islet have not been successful (35).

Experiments with anterograde and retrograde perfusion of rat pancreas with antibodies neutralizing insulin (36) or glucagon (37) gave rise to the proposal that intra-islet capillary blood flow is from the ß-cell core out to the {alpha}-cells. However, other studies on the islet microvasculature suggested that {alpha}-cells are perfused before the ß-cells (38). The present data indicate a close relation between the pulses of glucagon and insulin with a phase shift of approximately half the interpeak interval. Because of this antisynchrony, the maximal effect of glucagon on liver cells will occur at low concentrations of insulin. It is a matter for future studies to decide whether a disturbance of the temporal relation contributes to the development of diabetes.

There are two main families of purinoceptors, adenosine or P1 receptors and P2 receptors recognizing primarily ATP, ADP, UTP, and UDP (39). The P2 receptor family comprises two groups: the nucleotide-gated ion channel P2X receptors and G protein-coupled P2Y receptors. The purinoceptors involved in glucagon secretion differ from those known to affect insulin secretion. Comparing the effects of various purino derivatives at intermediate (8.3 mmol/liter) or low (2.8 mmol/liter) concentrations of glucose, it was reported that rat ß-cells respond to ATP and ADP by activation of P2Y receptors and that adenosine is the principal stimulator of {alpha}-cells via P1 receptors (40, 41). In experiments performed at 20 mol/liter glucose, we now observe that both ATP and the nonhydrolyzable ADP analog ADP-ß-S stimulate glucagon release, but adenosine is inhibitory. The complexity of purinoceptor regulation is illustrated from immunohistochemical studies indicating that rat {alpha}-cells express also P2X7 receptors (42, 43). The stimulation of glucagon release seen after addition of adenosine deaminase can reflect a degradation of intrinsic adenosine. However, at the concentration tested, adenosine deaminase may have effects independent of the enzyme activity, as suggested from its inhibitory action on insulin release.

It was early proposed that intrapancreatic ganglia serve as pacemakers for pulsatile release of islet hormones into the portal vein (44, 45). The observation that hormone-producing islet cells have an intrinsic ability to generate oscillations of [Ca2+]i urges a reevaluation of how autonomic nerves entrain the cells into a common rhythm. Evidence has been provided that ß-cells act in synchrony within an islet and that the different islets are locked into the same phase by nerves (12). It is important to note that nerve signals are not a prerequisite for oscillations but serve as coupling factors for coordinating an intrinsic rhythmicity via alterations in the membrane potential.

External ATP has a number of effects, reflecting the types of purinoceptors expressed and the species involved. Evaluating the role of the P2Y1 receptor, it was found that low concentrations of the specific inhibitor MRS 2179 interfered with the signal transfer between mouse ß-cells (10). Moreover, addition of MRS 2179 removed the pulsatility of insulin in the perfused rat pancreas with maintenance of the synchronization of the [Ca2+]i oscillations in aggregates of ß-cells (21). Pancreatic ganglia resemble enteric ganglia (45), which are known to express P2Y1 receptors (46). The observation that MRS 2179 prevents not only insulin but also glucagon pulses reinforces the arguments that neural P2Y1 receptors are important for coordinating the secretory activity of the islets.

Addition of MRS 2179 had opposing effects on the amounts of glucagon and insulin released in the presence of 20 mmol/liter glucose. The observation that glucagon release was suppressed by MRS 2179 and stimulated by ADP-ß-S indicates that P2Y1 receptors are important for the secretory activity of the {alpha}-cells. In the case of insulin, the stimulatory effect of MRS 2179 can be attributed to counteraction of the inhibitory effects of ATP accumulating around the ß-cells (21).


   Acknowledgments
 
We thank Dr. Michael Johnson, Pharmacological Department, University of Virginia Health Science Center, for providing software. The technical assistance of Britt-Marie Nilsson is gratefully acknowledged.


   Footnotes
 
This work was supported by the Swedish Research Council (72X-562, 12X-6240, and 04X-20029), the Swedish Diabetes Association, The Novo Nordic Fund, the Albert Påhlsson Foundation, the Crafoord Foundation, and the Family Ernfors Foundation.

Author Disclosure: E.G., A.S., S.Q., and B.H. have nothing to declare.

First Published Online April 13, 2006

Abbreviation: ADP-ß-S, Adenosine-5-O-2-thiodiphosphate.

Received November 15, 2005.

Accepted for publication April 6, 2006.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Lefèbvre PJ, Paolisso G, Scheen AJ, Henquin JC 1987 Pulsatility of insulin and glucagon release: physiological significance and pharmacological implications. Diabetologia 30:443–452[CrossRef][Medline]
  2. Pørksen N 2002 The in vivo regulation of pulsatile insulin secretion. Diabetologia 45:3–20[CrossRef][Medline]
  3. Grapengiesser E, Gylfe E, Hellman B 1988 Glucose-induced oscillations of cytoplasmic Ca2+ in the pancreatic ß-cell. Biochem Biophys Res Commun 151:1299–1304[CrossRef][Medline]
  4. Berts A, Gylfe E, Hellman B 1995 Ca2+ oscillations in pancreatic islet cells secreting glucagon and somatostatin. Biochem Biophys Res Commun 208:644–649[CrossRef][Medline]
  5. Berts A, Ball A, Gylfe E, Hellman B 1996 Suppression of Ca2+ oscillations in glucagon-producing {alpha}2 cells by insulin/glucose and amino acids. Biochim Biophys Acta 1310:212–216[Medline]
  6. Berts A, Ball A, Dryselius S, Gylfe E, Hellman B 1996 Glucose stimulation of somatostatin-producing islet cells involves oscillatory Ca2+ signaling. Endocrinology 137:693–697[Abstract]
  7. Liu Y, Hellman B, Gylfe E 1999 Ca2+ signaling in mouse pancreatic polypeptide cells. Endocrinology 140:5524–5529[Abstract/Free Full Text]
  8. Ravier M, Guldenagel M, Charollais A, Gjinovci A, Caille D, Sohl G, Wollheim C, Willecke K, Henquin J, Meda P 2005 Loss of connexin36 channels alters ß-cell coupling, islet synchronization of glucose-induced Ca2+ and insulin oscillations, and basal insulin release. Diabetes 54:1798–1807[Abstract/Free Full Text]
  9. Grapengiesser E, Gylfe E, Dansk H, Hellman B 2001 Nitric oxide induces synchronous Ca2+ transients in pancreatic ß-cells lacking contact. Pancreas 23:387–392[CrossRef][Medline]
  10. Hellman B, Dansk H, Grapengiesser E 2004 Pancreatic ß-cells communicate via intermittent release of ATP. Am J Physiol Endocrinol Metab 286:E759–E765
  11. Bergsten P, Hellman B 1993 Glucose-induced amplitude regulation of pulsatile insulin secretion from individual pancreatic islets. Diabetes 42:670–674[Abstract]
  12. Grapengiesser E, Dansk H, Hellman B 2004 Pulses of external ATP aid to the synchronization of pancreatic ß-cells by generating premature Ca2+ oscillations. Biochem Pharmacol 68:667–674[CrossRef][Medline]
  13. Unger R 1985 Glucagon physiology and pathophysiology in the light of new advances. Diabetologia 28:574–578[Medline]
  14. Pipeleers D, Schuit FC, Van Schravendijk C, Van de Winkel M 1985 Interplay of nutrients and hormones in the regulation of glucagon release. Endocrinology 117:817–823[Abstract]
  15. Göpel S, Kanno T, Barg S, Weng X, Gromada J, Rorsman P 2000 Regulation of glucagon secretion in mouse {alpha}-cells by KATP channels and inactivation of TTX-insensitive Na+ channels. J Physiol (Lond) 528:509–520[Abstract/Free Full Text]
  16. Liu Y, Vieira E, Gylfe E 2004 A store-operated mechanism determines the activity of the electrically excitable glucagon-secreting pancreatic {alpha}-cell. Cell Calcium 35:357–365[CrossRef][Medline]
  17. Ravier M, Rutter GA 2005 Glucose or insulin, but not zinc ions, inhibit glucagon secretion from mouse pancreatic {alpha}-cells. Diabetes 54:1789–1797[Abstract/Free Full Text]
  18. Franklin I, Gromada J, Gjinovci A, Theander S, Wollheim CB 2005 ß-Cell secretory products activate {alpha}-cell ATP-dependent potassium channels to inhibit glucagon release. Diabetes 54:1808–1815[Abstract/Free Full Text]
  19. Cejvan K, Coy D, Efendic S 2003 Intra-islet somatostatin regulates glucagon release via type 2 somatostatin receptors in rats. Diabetes 52:1176–1181[Abstract/Free Full Text]
  20. Grapengiesser E, Dansk H, Hellman B 2003 Synchronization of pancreatic ß-cell rhythmicity after glucagon induction of Ca2+ transients. Cell Calcium 34:49–53[CrossRef][Medline]
  21. Salehi A, Qader S, Grapengiesser E, Hellman B 2005 Inhibition of purinoceptors amplifies glucose-stimulated insulin release with removal of its pulsatility. Diabetes 54:2126–2131[Abstract/Free Full Text]
  22. Herbert V, Lau K, Gottleb C, Bleicher S 1965 Coated charcoal immunoassay of insulin. J Clin Endocrinol Metab 25:1375–1384[Medline]
  23. Salehi A, Carlberg M, Henningsson R, Lundquist I 1996 Islet constitutive nitric oxide synthase: biochemical determination and regulatory function. Am J Physiol 270:C1634–C1641
  24. Veldhuis J, Johnson M 1986 Cluster analysis: a simple,versatile and robust algorithm for endocrine pulse detection. Am J Physiol Endocrinol Metab 250:E486–E493
  25. Box G, Jenkins G 1976 Time series analysis: forecasting and control. Oakland, CA: Golden-Day; 532
  26. Olsen H, Theander S, Bokvist K, Buschard K, Wollheim C, Gromada J 2005 Glucose stimulates glucagon release in single rat {alpha}-cells by mechanisms that mirror the stimulus-secretion coupling in ß-cells. Endocrinology 146:4861–4870[Abstract/Free Full Text]
  27. Munoz A, Hu M, Hussain K, Bryan J, Aguilar-Bryan L, Rajan A 2005 Regulation of glucagon secretion at low glucose concentrations: evidence for adenosine triphosphate-sensitive potassium channel involvement. Endocrinology 146:5514–5521[Abstract/Free Full Text]
  28. Hansen B, Jen K, Pek S, Wolfe R 1982 Rapid oscillations in plasma insulin, glucagon and glucose in obese and normal weight humans. J Clin Endocrinol Metab 54:785–792[Abstract]
  29. Stagner J, Samols E 1992 The vascular order of islet cellular perfusion in the human pancreas. Diabetes 41:93–97[Abstract]
  30. Jaspan J, Lever E, Polonsky K, Van Cauter E 1986 In vivo pulsatility of pancreatic islet peptides. Am J Physiol 251:E215–E226
  31. Goodner C, Walike B, Koerker D, Ensinck J, Brown A, Chideckel E, Palmer J, Kalnasy L 1977 Insulin, glucagon, and glucose exhibit synchronous, sustained oscillations in fasting monkeys. Science 195:177–179[Abstract/Free Full Text]
  32. Lang D, Matthews D, Burnett M, Ward G, Turner R 1982 Pulsatile, synchronous basal insulin and glucagon secretion in man. Diabetes 31:22–26[Abstract]
  33. Michaels R, Sheridan JD 1981 Islets of Langerhans: dye coupling among immunocytochemically distinct cell types. Science 214:801–803[Abstract/Free Full Text]
  34. Meda P, Santos R, Atwater I 1986 Direct identification of electrophysiologically monitored cells within intact mouse islets of Langerhans. Diabetes 35:232–236[Abstract]
  35. Nadal A, Quesada I, Soria B 1999 Homologous and heterologous asynchrony between identified {alpha}-, ß- and {delta}-cells within intact islets of Langerhans in the mouse. J Physiol 517:85–93[Abstract/Free Full Text]
  36. Stagner JI, Samols E 1988 Comparison of insulin and glucagon pulsatile secretion between the rat and dog pancreas in-vitro. Life Sci 43:929–934[CrossRef][Medline]
  37. Stagner J, Samols E, Marks V 1989 The anterograde and retrograde infusion of glucagon antibodies suggests that A cells are vascularly perfused before D cells within the rat islet. Diabetologia 32:203–206[CrossRef][Medline]
  38. Brunicardi F, Stagner J, Bonner-Weir S, Wayland H, Kleinman R, Livingston E, Guth P, Menger M, McCuskey R, Intaglietta M, Charles A, Ashley S, Cheung A, Ipp E, Gilman S, Howard T, Passaro E 1996 Microcirculation of the islets of Langerhans. Long Beach Veterans Administration Regional Medical Education Center Symposium. Diabetes 45:385–392[Medline]
  39. Ralevic V, Burnstock G 1998 Receptors for purines and pyrimidines. Pharmacol Rev 50:413–492[Abstract/Free Full Text]
  40. Chapal J, Loubatières-Mariani M, Roye M, Zerbib A 1984 Effects of adenosine, adenosine triphosphate and structural analogues on glucagon secretion from the perfused pancreas of rat in vitro. Br J Pharmacol 83:927–933
  41. Loubatières-Mariani M, Chapal J 1988 Purinergic receptors involved in the stimulation of insulin and glucagon secretion. Diabetes Metab 14:119–126
  42. Coutinho-Silva R, Parsons M, Robson T, Burnstock G 2001 Changes in expression of P2 receptors in rat and mouse pancreas during development and ageing. Cell Tissue Res 306:373–383[CrossRef][Medline]
  43. Coutinho-Silva R, Parsons M, Robson T, Lincoln J, Burnstock G 2003 P2X and P2Y purinoceptor expression in pancreas from streptozotocin-diabetic rats. Mol Cell Endocrinol 204:141–154[CrossRef][Medline]
  44. Stagner JI, Samols E 1985 Perturbation of insulin oscillations by nerve blockade in the in vitro canine pancreas. Am J Physiol 248:E516–E521
  45. Stagner JI, Samols E 1985 Role of intrapancreatic ganglia in regulation of periodic insular secretions. Am J Physiol 248:E522–E530
  46. Giaroni C, Knight G, Ruan H, Glass R, Bardini M, Lecchini S, Frigo G, Burnstock G 2002 P2 receptors in the murine gastrointestinal tract. Neuropharmacology 43:1313–1323[CrossRef][Medline]



This article has been cited by other articles:


Home page
 Am. J. Physiol. Endocrinol. Metab.Home page
E. Tuduri, E. Filiputti, E. M. Carneiro, and I. Quesada
Inhibition of Ca2+ signaling and glucagon secretion in mouse pancreatic {alpha}-cells by extracellular ATP and purinergic receptors
Am J Physiol Endocrinol Metab, May 1, 2008; 294(5): E952 - E960.
[Abstract] [Full Text] [PDF]

Home page
 Physiol. Rev.Home page
G. Burnstock
Physiology and Pathophysiology of Purinergic Neurotransmission
Physiol Rev, April 1, 2007; 87(2): 659 - 797.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
147/7/3472    most recent
Author Manuscript (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Grapengiesser, E.
Right arrow Articles by Hellman, B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Grapengiesser, E.
Right arrow Articles by Hellman, B.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals