| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
ARTICLES |
Division of Endocrinology and Metabolism (K.B., H.A.L., J.C.G., J.D.V.), Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908; Department of Cell Biology and Biochemistry (D.M.S.), Texas Tech University Health Sciences Center, Lubbock, Texas 79430
Address all correspondence and requests for reprints to: Dr. Johannes D. Veldhuis, Division of Endocrinology and Metabolism, Box 202, Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In summary, two distinct first messenger regulatory molecules, FSH and IGF-I, interact synergistically to induce amplification of StAR messenger RNA and protein expression in serum-free monolayer cultures of immature (swine) granulosa cells.
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Recent cloning and transient transfection studies of the StAR complementary DNA (cDNA) in MA-10 (mouse Leydig tumor) cells showed that StAR expression conferred nearly a 3-fold increase in basal progesterone production compared with control cells transfected with vector alone, thus indicating a direct relationship between StAR expression and steroidogenesis (4, 7). Moreover, StAR messenger RNA (mRNA) and protein expression were acutely induced by trophic hormone stimulation in MA-10 cells (8). Studies on StAR gene expression in ovine corpora lutea showed high concentrations of StAR mRNA, which were stimulated by LH and GH. Furthermore, the physiologically varying luteal concentrations of mRNA encoding StAR were accompanied by corresponding changes in serum concentrations of progesterone (9).
Northern analysis of bovine StAR gene expression showed 3-kilobase pair (kb) and 1.8-kb transcripts, which are highly expressed in corpora lutea compared with adrenal gland, whereas no detectable expression was recorded in granulosa cells isolated from large preovulatory follicles (10). However, Sugawara et al. (11) have reported a major StAR mRNA transcript of 1.6 kb and less abundant transcripts of 4.4 and 7.5 kb in human ovary and testis. Three transcripts of 1.6, 2.7, and 3.4 kb for StAR mRNA have also been detected in MA-10 mouse Leydig tumor cells (8). Cultured human luteinized granulosa cells treated with 8-bromoadenosine 3',5'-cAMP (8-bromo-cAMP) responded with an increase of 3-fold or more in StAR mRNA accumulation at 24 h suggesting the presence of cAMP-responsive elements in StAR gene promoter region (11, 12). Finally, the identification of functionally relevant mutations in the StAR gene cloned from patients suffering from congenital lipoid adrenal hyperplasia associated with markedly impaired adrenal and gonadal steroidogenesis (5) has established the significant role of StAR in human steroidogenesis.
In view of the importance of StAR in basal and hormonally regulated steroidogenesis and the limited knowledge of FSH and growth factor regulation of this gene in gonadal cells, we undertook studies to determine the effects of FSH and/or insulin-like growth factor I (IGF-I) on StAR gene expression. These two trophic molecules are intimately involved in the maturation and differentiation of granulosa cells towards a progesterone-secreting phenotype, which would presumptively require StAR message and protein expression.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Cell culture
Granulosa cells were isolated from small and medium-sized (1–5
mm) follicles of immature (60–70 kg) swine by fine needle aspiration
(13). Cells were washed three times by low speed centrifugation (3000
rpm) in Eagle’s MEM, and approximately 4 x 107
viable granulosa cells were plated in 10-cm culture dishes (Corning,
Corning, NY) containing bicarbonate-buffered MEM and initially 3% FCS
(GIBCO, Grand Island, NY) to permit cell anchorage. Granulosa cells
were allowed to attach to culture dishes for 16–24 h at 37 C and 5%
CO2. Following the attachment period, cells were maintained
in serum-free MEM supplemented with antibiotics with the indicated
treatments for the designated time interval.
RNA isolation
RNA pooled from three to five dishes contributed to each
experimental replicate. Total RNA was isolated from harvested cells as
previously described (13) using the method of Chirgwin et
al. (14). RNA pellets were ethanol precipitated, washed, and
resuspended in sterile water, and quantitated spectrophotometrically by
absorbance at 260/280 nm in a Spectronics model 601
spectrophotometer.
Mitochondrial protein isolation
Mitochondrial protein pooled from six dishes contributed to each
experimental replicate. For protein isolation, granulosa cells were
harvested from culture dishes by scraping with a rubber policeman into
5 ml buffer containing 0.25 M sucrose, 10 mM
Tris, 0.1 mM EDTA (pH 7.4). Cells were processed
immediately or frozen at -70 C for later processing. Cells were
homogenized on ice using 20 strokes in a Dounce homogenizer. Lysates
were centrifuged at 600 x g for 15 min at 4 C. The
supernatant was centrifuged at 10,000 x g for 15 min
at 4 C and the resulting pellet resupended in 1 ml ice-cold buffer. A
100-µl aliquot of this was saved for later protein quantitation by
using Bio-Rad protein dye reagent (Bio-Rad Laboratories, Hercules, CA).
The remaining mitochondrial resuspension was pelleted by centrifugation
at 10,000 x g for 15 min at 4 C. The mitochondrial
pellet was frozen at -70 C and then lyophilized. Western analysis was
performed as previously described using a mouse polyclonal StAR
antibody (4) and 300 µg of granulosa cell mitochondrial protein.
Generation of porcine StAR cDNA riboprobe
A partial porcine cDNA sequence was cloned from porcine corpora
lutea RNA by RT-PCR. The 280-bp cDNA was amplified using primers
corresponding to mouse sequence bases 442–461 and 702–722 (4). RT-PCR
was performed using the GENEAMP RNA PCR kit (Perkin-Elmer/Cetus,
Norwalk, CT), and a single band of expected size was amplified and
purified on low melt agarose gel and extracted on Wizard PCR Prep
minicolumns (Promega Corp., Madison, WI). The DNA band was subcloned
into the TA PCRII cloning vector (Invitrogen Corp., San Diego, CA) and
transformed into competent INV-
F' strain of Escherichia
coli. The insert was sequenced manually by the dideoxynucleotide
chain termination method (Sequenase version 2 kit, U.S. Biochemical
Corp., Cleveland, OH). Both strands were fully sequenced. The sequence
was confirmed by an automated sequencer (Biomolecular Research
Facility, University of Virginia, Charlottesville, VA). Two separate
tissue preparations pooled from three or more animals were analyzed by
PCR and independently sequenced to confirm reproducibility.
Solution hybridization/RNase protection assay
RNase protection assays were performed using the RPA II kit
(Ambion, Austin, TX). The StAR antisense riboprobe (complementary
RNA), approximately 376 bases in length, was transcribed using the
Maxiscript in vitro transcription kit (Ambion). Before
transcription, the DNA template was linearized with EcoRV.
Transcription was carried out for 1 h at room temperature using 1
µg DNA template with [32P]UTP and SP6 polymerase. Large
quantities of very low specific activity (2500 dpm/µg) human 18S
ribosomal RNA antisense riboprobe were synthesized using Ambion’s pT7
RNA 18S template, T7 polymerase, and the MEGAscript in vitro
transcription kit. Labeled riboprobes were purified using Sephadex G-50
minispin columns (Worthington Biochemical Corp., Freehold, NJ).
Preliminary experiments were performed to determine saturating
quantities of each riboprobe used in subsequent experiments. Total RNA
(10 µg) from granulosa cells was resuspended in hybridization buffer
containing saturating concentrations of high specific activity StAR
riboprobe and low specific activity 18S riboprobe. The mixture was
heated to 90 C for 4 min, and samples were hybridized for 18 h at
45 C. Subsequently, samples were treated with RNase A/T1 mixture for 30
min at 37 C, precipitated, and resuspended in formamide-containing gel
loading buffer, and run on 8% polyacrylamide-8 M urea
gels. Gels were exposed overnight and up to three days to Fuji RX film
at -70 C with intensifying screens. Protected RNA bands were
quantitated by laser densitometry using ImageQuant software and
densitometer (Molecular Dynamics, Sunnyvale, CA).
Other analytical methods
Progesterone concentrations in culture medium were measured by
RIA using antibody-coated tubes manufactured by ICN Biomedicals (Costa
Mesa, CA). The RIA has a sensitivity of 0.15 ng/ml and less than 1%
cross-reactivity with other relevant steroid hormones, including
estradiol and 17-hydroxyprogesterone (13).
Statistical methods
Unless noted, all data are presented as mean ±
SEM of three or more independent experiments using separate
batches of 200–300 ovaries to confirm the reproducibility of results.
To adjust for nonhomogeneous variances in the StAR message data, values
were transformed by multiplying by a factor of 10 and converting each
to a natural log value and subjecting these values to ANOVA. Treatments
were evaluated post hoc by the Tukey HSD multiple comparison
test. Time course mRNA data were likewise
log-transformed and submitted to regression analysis. Progesterone data
were used untransformed for ANOVA followed by the Tukey HSD test (15).
Because control StAR protein values were not detectable in two out of
three experiments, treatment protein values could not be normalized for
control in each experiment, and therefore were not statistically
analyzed. Fold increases (relative to control) in protein were
calculated from the mean values for the three experiments.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The time course of the actions of FSH, IGF-I, and FSH plus IGF-I on StAR mRNA accumulation was investigated by culturing granulosa cells for 6, 12, 24, and 48 h in the presence of serum-free medium alone, FSH (100 ng/ml), IGF-I (100 ng/ml), or FSH plus IGF-I. The time course was initiated after cell attachment; then, cells were maintained in serum-free medium for a total of 48 h. Six, 12, 24, and 48 h before termination of this incubation, the indicated effectors or vehicle were added to the cultures.
All hormone treatments produced significant time-dependent stimulation
of progesterone production, demonstrating the functional responsiveness
of these immature granulosa cells to these hormones (Fig. 1A
). As shown in Fig. 1B, hybridization with
[32P]-labeled StAR complementary RNA, followed by RNase
digestion and PAGE, resulted in protected StAR and 18S ribosomal RNA
bands corresponding to sizes of approximately 280 and a 70/80 bp
doublet, respectively. Figure 1C graphically summarizes the
quantitative densitometry results of these replicated studies.
Treatment with FSH or IGF-I alone had only a small effect on StAR
message accumulation at any time during the 48 h studied. However,
each hormone (FSH, three of three experiments; IGF-I, five of five
experiments) alone produced a consistent small increase (1.6- to
2.7-fold) in StAR mRNA at 48 h. Moreover, the combined effect of
FSH plus IGF-I was significant by 24 h and maximal at 48 h
(P < 0.001).
|
gives a representative autoradiogram showing the effects of 48 h
treatment with FSH (100 ng/ml), IGF-I (100 ng/ml), 8-bromo-cAMP (1
mM) and their relevant combinations on granulosa cell StAR
mRNA accumulation. Treatment of granulosa cells with 8-bromo-cAMP alone
(like FSH) had only a small stimulatory effect on mRNA levels encoding
StAR (3.5-fold) (Fig. 2B). However, in three experiments, when combined
with IGF-I (100 ng/ml), the synergistic effect of the cAMP agonist
(40-fold) was comparable with that observed in FSH plus IGF-I treated
cells (26-fold). Granulosa cells were steroidogenically responsive to
8-bromo-cAMP during the 48 h culture period with a mean
progesterone accumulation (ng/ml) of 409 ± 13 for 8-bromo-cAMP
alone and 512 ± 77 when combined with IGF-I.
|
. Similar to StAR
mRNA accumulation, StAR protein expression was markedly increased in
FSH plus IGF-I and 8-bromo-cAMP plus IGF-I treated granulosa cells more
than 56- to 60-fold for the three experiments considered together,
whereas IGF-I and 8-bromo-cAMP alone elicited small increases (at least
6- and 3.7-fold, respectively), and FSH did not increase protein
levels. Increases were at least the "fold" values
indicated because control lanes were undetectable in two of three
experiments. These data demonstrate that StAR mRNA, protein, and
progesterone biosynthesis are induced concomitantly and that this
likely occurs in part via a cAMP-mediated mechanism, wherein FSH or
cAMP synergize with IGF-I actions.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
As mentioned above, Northern analysis has revealed two or three transcripts of StAR in other species. RNase protection analysis with our porcine probe, which spans the equivalent of exons 4 and 5 in the corresponding sequence of the mouse cDNA, would not detect transcripts that differ at the 3' or 5' ends but is a quantitative estimate of total StAR message coding sequence. Recently, Northern analysis using a mouse StAR cDNA has revealed two transcripts in porcine ovary and testes of approximately 1.5 and 2.8 kb, with the larger transcript being more predominant (16). It is not known whether trophic hormones or growth factors can differentially regulate the transcripts of the StAR message.
An acute action of trophic hormones on steroidogenic cells is to mobilize and deliver cholesterol, the precursor substrate for steroid hormone biosynthesis, to the mitochondrial inner membrane, where it is metabolized to pregnenolone by the cytochrome P450 cholesterol side-chain cleavage enzyme complex (3, 17). Early studies indicated that puromycin or cycloheximide, inhibitors of protein synthesis, blocked trophic hormone-stimulated acute steroidogenesis without affecting the activity of P450scc or the delivery of cholesterol to the outer mitochondrial membrane (18, 19, 20). Such experiments suggested the involvement of newly synthesized protein in the translocation of cholesterol to the inner mitochondrial membrane (21). Recently, the StAR gene was cloned as a plausible mediator of this process (4).
Hormonally untreated sparingly differentiated pig granulosa cells revealed little detectable basal expression of StAR mRNA and protein in the present study. This finding is consistent with recent observations in unstimulated bovine granulosa cells (10). Swine granulosa cells treated with PKA agonist, 8-bromo-cAMP, or IGF-I alone for 48 h showed an average of 3.5- or 2.7-fold increase in StAR mRNA accumulation, respectively, compared with untreated cells. The combined actions of 8-bromo-cAMP and IGF-I yielded a 40-fold increase in StAR message indicating prominent synergism in the regulation of this gene transcript. In accordance with the present results, recently Sugawara et al. (11) also reported stimulatory effects of cAMP analogue treatment (for 24 h) on StAR message expression in luteinized human granulosa cells. Importantly, in the present study immunoblot analysis of the StAR protein also disclosed prominent synergistic actions of IGF-I plus FSH or 8-bromo-cAMP, thus indicating effective StAR mRNA translation as well.
Many actions of gonadotropic hormones, including FSH, on steroidogenic cells are mediated at least in part by cAMP activation of PKA (22, 23). Thus we used the PKA agonist, 8-bromo-cAMP to determine if it could mimic the FSH effect on StAR message and protein expression. In the present investigation, 48 h treatment of primary cultures of porcine granulosa cells with FSH, 8-bromo-cAMP, and IGF-I had modest individual effects on StAR message accumulation when compared with the combination of FSH or 8-bromo-cAMP with IGF-I. The combination of either PKA activator with IGF-I evoked a marked time-dependent synergism. Qualitatively similar synergism was reported in porcine granulosa cells with respect to 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase message accumulation (24), although the magnitudes of these interactions varied. The mechanisms which underlie this synergism putatively involve FSH’s stimulation of cAMP and the PKA pathway on the one hand, and IGF’s activation of its receptor tyrosine kinase and associated signals on the other hand. Where these signaling pathways interact to ultimately increase expression of the StAR gene transcript is not yet known. However, this interaction is likely to be of major physiological importance because the intrafollicullar presence of immunoreactive IGF-I, its receptor, binding proteins, and trophic effects of IGF’s on ovarian cells have all been documented (25, 26, 27, 28, 29). IGF-I binds and activates an intrinsic tyrosine kinase activity of high-affinity, saturable, low-capacity receptors in porcine granulosa cells (30, 31). Further, FSH stimulates IGF-I production by and binding to granulosa cells (25, 32). Although in some species such as the pig IGF-I is able to stimulate progesterone biosynthesis alone, in many species it markedly enhances FSH-stimulated steroidogenesis, granulosa-cell cytodifferentiation, and LH receptor formation in part by increasing FSH-induced cAMP accumulation as well as via actions at post-cAMP loci (28, 33, 34, 35, 36, 37). Therefore, the synergistic influence of FSH and IGF-I on StAR mRNA accumulation could reflect stimulatory interactions of these hormones at one or more levels, such as hormone binding, activation of second messengers, and distal intracellular cascades of molecular events that control specific gene expression in differentiating granulosa cells.
Interestingly, progesterone concentrations in our FSH or IGF-I alone treated granulosa cell cultures increased significantly in 48 h, whereas StAR mRNA accumulation or StAR protein expression only rose to a small extent. This is in contrast to time-course studies done in MA-10 Leydig tumor cells where 8-bromo-cAMP induced steroid production that paralleled StAR expression (4). The failure to increase progesterone synthesis in vitro equivalently to StAR transcripts may reflect the need of porcine granulosa cells for lipoprotein-borne cholesterol substrate to maximize steroidogenesis in serum-free conditions. In this regard, the FSH plus IGF-I synergism also was expressed at the level of mRNA and protein, but not progesterone production, at least under the present serum-free and lipoprotein-free in vitro culture conditions. Indeed, addition of swine or human low density lipoprotein allows remarkable (100-fold) FSH/IGF-I synergism in progesterone production by these cells (37). Relatively low stability of StAR message or protein in FSH or IGF-I treated cells compared with FSH plus IGF-I treated cells could also account for our findings. Whether enhanced StAR mRNA accumulation observed in the present studies is the direct consequence of increased transcription, heightened message stability, or both, remains to be established. For example, the increase in StAR mRNA accumulation in FSH and IGF-I treated swine granulosa cells may result from increased StAR gene promoter activity. In the porcine P450scc enzyme promoter, these two hormones promote transcription via a common site in the 5'-flanking region of the gene (38). In addition, like the P450scc enzyme and other steroid hydroxylases, a SF-1 site(s) is present in both the murine and human StAR promoters and contributes to transcriptional regulation (8, 12). Further investigation of the regulatory mechanisms of StAR gene expression will be necessary to unravel the molecular messengers that mediate FSH and IGF-I’s synergism in granulosa cells.
In conclusion, StAR gene expression in primary cultures of porcine granulosa cells is stimulated above control levels by FSH, 8-bromo-cAMP, or IGF-I individually, but 26- to 40-fold by the combined trophic effects of IGF-I and FSH (or 8-bromo-cAMP), thereby evincing a marked synergism. Similar results showing StAR mRNA and protein accumulation in FSH plus IGF-I or 8-bromo-cAMP plus IGF-I treated granulosa cells imply that IGF-I’s facilitation of FSH action on StAR gene expression may be mediated through activation of the distal PKA pathway. The synergistic regulation by FSH and IGF-I of StAR message and protein expression may prepare granulosa cells for the increased steroidogenic demand imposed during the later stages of granulosa-luteal cell differentiation.
|
Footnotes |
|---|
2 On leave from the Department of Endocrinology, University of Madras,
Taramani, Madras, India 600 113.
Received August 19, 1996.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  Y.-J. Chen, M.-T. Lee, H.-C. Yao, P.-W. Hsiao, F.-C. Ke, and J.-J. Hwang Crucial Role of Estrogen Receptor-{alpha} Interaction with Transcription Coregulators in Follicle-Stimulating Hormone and Transforming Growth Factor {beta}1 Up-Regulation of Steroidogenesis in Rat Ovarian Granulosa Cells Endocrinology, September 1, 2008; 149(9): 4658 - 4668. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Seto-Young, D. Avtanski, M. Strizhevsky, G. Parikh, P. Patel, J. Kaplun, K. Holcomb, Z. Rosenwaks, and L. Poretsky Interactions among Peroxisome Proliferator Activated Receptor-{gamma}, Insulin Signaling Pathways, and Steroidogenic Acute Regulatory Protein in Human Ovarian Cells J. Clin. Endocrinol. Metab., June 1, 2007; 92(6): 2232 - 2239. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. R Manna, Y. Jo, and D. M Stocco Regulation of Leydig cell steroidogenesis by extracellular signal-regulated kinase 1/2: role of protein kinase A and protein kinase C signaling J. Endocrinol., April 1, 2007; 193(1): 53 - 63. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. R Manna, S. P Chandrala, Y. Jo, and D. M Stocco cAMP-independent signaling regulates steroidogenesis in mouse Leydig cells in the absence of StAR phosphorylation. J. Mol. Endocrinol., August 1, 2006; 37(1): 81 - 95. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Campbell, J. Dickey, B. Beckman, G. Young, A. Pierce, H. Fukada, and P. Swanson Previtellogenic Oocyte Growth in Salmon: Relationships among Body Growth, Plasma Insulin-Like Growth Factor-1, Estradiol-17beta, Follicle-Stimulating Hormone and Expression of Ovarian Genes for Insulin-Like Growth Factors, Steroidogenic-Acute Regulatory Protein and Receptors for Gonadotropins, Growth Hormone, and Somatolactin Biol Reprod, July 1, 2006; 75(1): 34 - 44. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Rusovici, Y. Y. Hui, and H. A. LaVoie Epidermal Growth Factor-Mediated Inhibition of Follicle-Stimulating Hormone-Stimulated StAR Gene Expression in Porcine Granulosa Cells Is Associated with Reduced Histone H3 Acetylation Biol Reprod, April 1, 2005; 72(4): 862 - 871. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. A. LaVoie, D. Singh, and Y. Y. Hui Concerted Regulation of the Porcine Steroidogenic Acute Regulatory Protein Gene Promoter Activity by Follicle-Stimulating Hormone and Insulin-Like Growth Factor I in Granulosa Cells Involves GATA-4 and CCAAT/Enhancer Binding Protein {beta} Endocrinology, July 1, 2004; 145(7): 3122 - 3134. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Sugawara, H. Shimizu, N. Hoshi, A. Nakajima, and S. Fujimoto Steroidogenic Acute Regulatory Protein-binding Protein Cloned by a Yeast Two-hybrid System J. Biol. Chem., October 24, 2003; 278(43): 42487 - 42494. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Gillio-Meina, Y. Y. Hui, and H. A. LaVoie GATA-4 and GATA-6 Transcription Factors: Expression, Immunohistochemical Localization, and Possible Function in the Porcine Ovary Biol Reprod, February 1, 2003; 68(2): 412 - 422. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Zaczek, J. Hammond, L. Suen, S. Wandji, D. Service, A. Bartke, V. Chandrashekar, K. Coschigano, and J. Kopchick Impact of Growth Hormone Resistance on Female Reproductive Function: New Insights from Growth Hormone Receptor Knockout Mice Biol Reprod, October 1, 2002; 67(4): 1115 - 1124. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Eimerl and J. Orly Regulation of Steroidogenic Genes by Insulin-Like Growth Factor-1 and Follicle-Stimulating Hormone: Differential Responses of Cytochrome P450 Side-Chain Cleavage, Steroidogenic Acute Regulatory Protein, and 3{beta}-Hydroxysteroid Dehydrogenase/Isomerase in Rat Granulosa Cells Biol Reprod, September 1, 2002; 67(3): 900 - 910. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Johnson and J. T. Bridgham Regulation of Steroidogenic Acute Regulatory Protein and Luteinizing Hormone Receptor Messenger Ribonucleic Acid in Hen Granulosa Cells Endocrinology, July 1, 2001; 142(7): 3116 - 3124. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. F. Palter, A. B. Tavares, A. Hourvitz, J. D. Veldhuis, and E. Y. Adashi Are Estrogens of Import to Primate/Human Ovarian Folliculogenesis? Endocr. Rev., June 1, 2001; 22(3): 389 - 424. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T.-J. Huang and P. Shirley Li Dexamethasone Inhibits Luteinizing Hormone-Induced Synthesis of Steroidogenic Acute Regulatory Protein in Cultured Rat Preovulatory Follicles Biol Reprod, January 1, 2001; 64(1): 163 - 170. [Abstract] [Full Text]
|
|
|
|
|
|
N. Sekar, H. A. LaVoie, and J. D. Veldhuis Concerted Regulation of Steroidogenic Acute Regulatory Gene Expression by Luteinizing Hormone and Insulin (or Insulin-Like Growth Factor I) in Primary Cultures of Porcine Granulosa-Luteal Cells Endocrinology, November 1, 2000; 141(11): 3983 - 3992. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Zhang, J. C. Garmey, and J. D. Veldhuis Interactive Stimulation by Luteinizing Hormone and Insulin of the Steroidogenic Acute Regulatory (StAR) Protein and 17{alpha}-Hydroxylase/17, 20-Lyase (CYP17) Genes in Porcine Theca Cells Endocrinology, August 1, 2000; 141(8): 2735 - 2742. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. C. L. Jayes, R. N. Day, J. C. Garmey, R. J. Urban, G. Zhang, and J. D. Veldhuis Calcium Ions Positively Modulate Follicle-Stimulating Hormone- and Exogenous Cyclic 3',5'-Adenosine Monophosphate-Driven Transcription of the P450scc Gene in Porcine Granulosa Cells Endocrinology, July 1, 2000; 141(7): 2377 - 2384. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Belin, G. Goudet, G. Duchamp, and N. Gérard Intrafollicular Concentrations of Steroids and Steroidogenic Enzymes in Relation to Follicular Development in the Mare Biol Reprod, May 1, 2000; 62(5): 1335 - 1343. [Abstract] [Full Text]
|
|
|
|
 |
|
 L. Devoto, L. K. Christenson, J. M. McAllister, A. Makrigiannakis, and J. F. Strauss III Insulin and insulin-like growth factor-I and- II modulate human granulosa-lutein cell steroidogenesis: enhancement of steroidogenic acute regulatory protein (StAR) expression Mol. Hum. Reprod., November 1, 1999; 5(11): 1003 - 1010. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Pescador, D. M. Stocco, and B. D. Murphy Growth Factor Modulation of Steroidogenic Acute Regulatory Protein and Luteinization in the Pig Ovary Biol Reprod, June 1, 1999; 60(6): 1453 - 1461. [Abstract] [Full Text]
|
|
|
|
|
|
M. Kanzaki and P. L. Morris Growth Hormone Regulates Steroidogenic Acute Regulatory Protein Expression and Steroidogenesis in Leydig Cell Progenitors Endocrinology, April 1, 1999; 140(4): 1681 - 1686. [Abstract] [Full Text]
|
|
|
|
|
|
R. Mamluk, Y. Greber, and R. Meidan Hormonal Regulation of Messenger Ribonucleic Acid Expression for Steroidogenic Factor-1, Steroidogenic Acute Regulatory Protein, and Cytochrome P450 Side-Chain Cleavage in Bovine Luteal Cells Biol Reprod, March 1, 1999; 60(3): 628 - 634. [Abstract] [Full Text]
|
|
|
|
|
|
A. Kerban, D. Boerboom, and J. Sirois Human Chorionic Gonadotropin Induces an Inverse Regulation of Steroidogenic Acute Regulatory Protein Messenger Ribonucleic Acid in Theca Interna and Granulosa Cells of Equine Preovulatory Follicles Endocrinology, February 1, 1999; 140(2): 667 - 674. [Abstract] [Full Text]
|
|
|
|
|
|
H. A. LaVoie, J. C. Garmey, and J. D. Veldhuis Mechanisms of Insulin-Like Growth Factor I Augmentation of Follicle-Stimulating Hormone-Induced Porcine Steroidogenic Acute Regulatory Protein Gene Promoter Activity in Granulosa Cells Endocrinology, January 1, 1999; 140(1): 146 - 153. [Abstract] [Full Text]
|
|
|
|
|
|
C. Mauduit, F. Gasnier, C. Rey, M.-A. Chauvin, D. M. Stocco, P. Louisot, and M. Benahmed Tumor Necrosis Factor-{alpha} Inhibits Leydig Cell Steroidogenesis through a Decrease in Steroidogenic Acute Regulatory Protein Expression Endocrinology, June 1, 1998; 139(6): 2863 - 2868. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Amsterdam and N. Selvaraj Control of Differentiation, Transformation, and Apop |
0.0001. B, Representative autoradiogram
showing time course experiments for StAR mRNA accumulation in porcine
granulosa cells treated with vehicle (C), FSH, IGF-I, or FSH plus
IGF-I. Ten-microgram aliquots of granulosa cell total RNA were
subjected to RNase protection assay as described in Materials
and Methods. Protected bands corresponding to StAR mRNA (280
bp) and 18S rRNA (70 and 80 bp doublet) are indicated on the right. C,
Histogram summary of time-course experiments for StAR mRNA accumulation
in porcine granulosa cells. Legends same as in panel A. Data are the
mean ± SEM from two to three experiments and
represent optical density units for StAR mRNA normalized to
constitutively expressed 18S rRNA and corrected for time = 0
(unstimulated) control. The inset shows the
log-transformed linear regressions of control and FSH plus IGF-I data.
The slope of each regression line ± SEM is indicated.
The Control response did not change significantly over time,
P = 0.81, whereas the FSH plus IGF-I treated cells
showed a significant time-dependent increase in StAR mRNA accumulation,
P = 0.001.
