Endocrinology, Vol 137, 3394-3400, Copyright © 1996 by Endocrine Society

ARTICLES

Adrenocorticotropin secretion by fetal sheep anterior and intermediate lobe pituitary cells in vitro: effects of gestation and adrenalectomy

MA Fora, TG Butler, JC Rose and J Schwartz
Department of Physiology, Bowman Gray School of Medicine, Winston- Salem, North Carolina 27157, USA.

Immunoreactive (ir) ACTH is present in the fetal sheep intermediate lobe (IL) as well as the anterior pituitary (AP). It is not clear whether fetal IL cells can secrete irACTH and if gestational age and glucocorticoids influence the secretion of ACTH from these tissues in a similar fashion. Therefore, we examined the control of irACTH secretion by IL cells, whether the responsiveness of AP and IL cells to arginine vasopressin (AVP) and CRH changes during gestation, and whether withdrawal of adrenal steroids by adrenalectomy influences AP and IL responses. Cultured pituitary cells were studied from intact fetuses at an immature (n = 5; 108 +/- 5 days) and a mature (n = 8; 139 +/- 0 days) stage, from mature fetuses 3 weeks after bilateral adrenalectomy (n = 6), and from neonatal lambs within 16 h of birth (n = 6). Secretion of irACTH was determined by RIA of incubation medium obtained during 3-h exposure of cells to vehicle, AVP, CRH, or both. In all cases, IL cells secreted measurable irACTH. The IL cells of immature fetuses responded to CRH (133 +/- 8% increase over basal secretion), AVP (52 +/- 6%), and CRH plus AVP (244 +/- 8%). In contrast, IL cells from mature fetuses responded only to CRH (160 +/- 20%) or CRH plus AVP (259 +/- 44%), as did cells from mature adrenalectomized fetuses (CRH, 356 +/- 70%; CRH plus AVP, 627 +/- 100%). Secretion from neonatal IL cells was not significantly increased above basal rates by CRH and/or AVP. The AP cells from immature fetuses responded significantly to CRH (406 +/- 16%), AVP (114 +/- 8%), and CRH plus AVP (559 +/- 38%), whereas cells from mature fetuses responded only to AVP (249 +/- 40%) or to CRH plus AVP (570 +/- 146%). In AP cells from mature adrenalectomized fetuses, the response pattern resembled that of immature intact fetal sheep (CRH, 429 +/- 76%; AVP, 146 +/- 15%; CRH plus AVP, 541 +/- 94%). Neonatal AP cells responded to CRH (196 +/- 25%), AVP (442 +/- 71%), and CRH plus AVP (646 +/- 93%). Further characterization of IL cells (n = 6 fetal and 2 neonatal) indicated that they were inhibited by dopamine (basal ACTH secretion decreased by 25 +/- 4%; ACTH secretory response to CRH decreased by 32 +/- 10%). These results show that fetal neurointermediate lobe cells secrete irACTH under basal and stimulated conditions. Moreover, the pattern of response of AP and neurointermediate lobe cells to secretagogues is influenced by gestational age and, possibly, cortisol.

This article has been cited by other articles:

				C. A. Ducsay, M. Mlynarczyk, K. M. Kaushal, K. Hyatt, K. Hanson, and D. A. Myers Long-term hypoxia enhances ACTH response to arginine vasopressin but not corticotropin-releasing hormone in the near-term ovine fetus Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2009; 297(3): R892 - R899. [Abstract] [Full Text] [PDF]

				L. C. Carey, S. B. Tatter, and J. C. Rose Cortisol infusion in late-gestation hypothalamo-pituitary disconnected sheep fetus restores pituitary cell responsiveness to arginine vasopressin Am J Physiol Endocrinol Metab, February 1, 2009; 296(2): E300 - E304. [Abstract] [Full Text] [PDF]

				L. C. Carey, S. B. Tatter, and J. C. Rose Ontogeny and Effects of Hypothalamic Pituitary Disconnection on Formation of Inositol Trisphosphate in Fetal Sheep Pituitary Cells Endocrinology, March 1, 2007; 148(3): 1440 - 1444. [Abstract] [Full Text] [PDF]

				K. Farrand, I. C. McMillen, S. Tanaka, and J. Schwartz Subpopulations of Corticotrophs in the Sheep Pituitary during Late Gestation: Effects of Development and Placental Restriction Endocrinology, October 1, 2006; 147(10): 4762 - 4771. [Abstract] [Full Text] [PDF]

				S. F. Young, S. B. Tatter, N. K. Valego, J. P. Figueroa, J. Thompson, and J. C. Rose The role of hypothalamic input on corticotroph maturation in fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2003; 284(6): R1621 - R1630. [Abstract] [Full Text] [PDF]

				S. F. Young, J. C. Rose, and J. Schwartz Ontogeny of Corticotropin-Releasing Hormone Binding in Anterior Pituitaries of Fetal Sheep Reproductive Sciences, April 1, 2003; 10(3): 130 - 135. [Abstract] [PDF]

				S. F. Young, J. L. Smith, J. P. Figueroa, and J. C. Rose Ontogeny and effect of cortisol on vasopressin-1b receptor expression in anterior pituitaries of fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2003; 284(1): R51 - R56. [Abstract] [Full Text] [PDF]

				J. L. Green, J. P. Figueroa, G. A. Massmann, J. Schwartz, and J. C. Rose Corticotropin-Releasing Hormone Type I Receptor Messenger Ribonucleic Acid and Protein Levels in the Ovine Fetal Pituitary: Ontogeny and Effect of Chronic Cortisol Administration Endocrinology, August 1, 2000; 141(8): 2870 - 2876. [Abstract] [Full Text] [PDF]

				D. A. Myers, M. E. Bell, T. J. McDonald, and T. R. Myers Corticotropin-Releasing Factor Receptor Expression in the Pituitary of Fetal Sheep after Lesion of the Hypothalamic Paraventricular Nucleus Endocrinology, September 1, 1999; 140(9): 4292 - 4299. [Abstract] [Full Text]

				T G Butler, J Schwartz, and I C McMillen Functional heterogeneity of corticotrophs in the anterior pituitary of the sheep fetus J. Physiol., May 1, 1999; 516(3): 907 - 913. [Abstract] [Full Text] [PDF]

				M. E. Bell, T. R. Myers, and D. A. Myers Expression of Proopiomelanocortin and Prohormone Convertase-1 and -2 in the Late Gestation Fetal Sheep Pituitary Endocrinology, December 1, 1998; 139(12): 5135 - 5143. [Abstract] [Full Text] [PDF]

				T. M. Jeffray, S. G. Matthews, G. L. Hammond, and J. R. G. Challis Divergent changes in plasma ACTH and pituitary POMC mRNA after cortisol administration to late-gestation ovine fetus Am J Physiol Endocrinol Metab, March 1, 1998; 274(3): E417 - E425. [Abstract] [Full Text] [PDF]

				J. Schwartz and J. C. Rose Development of the pituitary adrenal axis in fetal sheep twins Am J Physiol Regulatory Integrative Comp Physiol, January 1, 1998; 274(1): R1 - R8. [Abstract] [Full Text] [PDF]

				M. E. Bell, T. R. Myers, T. J. McDonald, and D. A. Myers Fetal Sheep Pituitary Proopiomelanocortin in Late Gestation: Effect of Bilateral Lesions of the Paraventricular Nucleus on Regional and Cellular Messenger Ribonucleic Acid Levels Endocrinology, September 1, 1997; 138(9): 3873 - 3880. [Abstract] [Full Text] [PDF]

				F. M. Perez, J. Schwartz, and J. C. Rose Developmental Changes in Ovine Corticotrophs in Vitro Endocrinology, March 1, 1997; 138(3): 916 - 921. [Abstract] [Full Text] [PDF]