Endocrinology, Vol 108, 2114-2119, Copyright © 1981 by Endocrine Society

ARTICLES

Maturation of adrenocorticotropin-sensitive adenylate cyclase of ovine fetal adrenal during late pregnancy

P Durand, AM Cathiard, AM Morera, A Dazord and JM Saez

The number of ACTH-(1-24) receptors and the adenylate cyclase (AC) responsiveness to several stimuli have been measured in crude adrenal membranes from fetal and newborn lambs. At 124 days of gestation, the number of ACTH-(1-24)-binding sites was 51 +/- 9 (SE) pmol/microgram DNA, and AC was stimulated by 2 x 10(-2) M NaF (195 +/- 5%) and 10(-5) M guanosine (beta, gamma-imido) triphosphate [Gpp(NH)p]; (168 +/- 8%) but not by 10(-6) M ACTH-(1-24). However, when Gpp(NH)p was added to ACTH-(1-24), the response was significantly higher than with Gpp(NH)p alone. On the contrary, at 140 days, despite no increase in the number of ACTH-(1-24) receptors, AC was stimulated by ACTH-(1-24) (135 +/- 6%), and Gpp(NH)p enhanced this response. In addition, the response to NaF and to Gpp(NH)p alone was higher at 140 than at 124 days. Between day 140 of gestation and birth, the stimulation of AC by ACTH-(1-24) and ACTH-(1-24) plus Gpp(NH)p increased, but the response to NaF and to Gpp(NH)p alone did not. During the same time, the number of ACTH-(1-24) receptors was increased by a factor of 3. No change in the Kd and Km of ACTH-(1-24) was observed during the period studied. Neither prostaglandin E2 (10(-5) M) nor alpha MSH (10(-6) M) stimulated AC at any stage. The relative insensitivity of AC before 140 days can thus be related to 1) a defect of availability of GTP, and 2) a low activity of the catalytic subunit of AC (subunit C) or, alternatively, a defect in the GTP-binding component (subunit N). The increased sensitivity to ACTH-(1-24) of the enzyme just before parturition correlates closely with an increase in the number of ACTH-(1-24) receptors.

This article has been cited by other articles:

				Yixin Su and J. C. Rose The Impact of ACTH Receptor Knockdown on Fetal and Adult Ovine Adrenocortical Cell Function Reproductive Sciences, March 1, 2008; 15(3): 253 - 262. [Abstract] [PDF]

				Y. Su, L. C. Carey, N. K. Valego, and J. C. Rose Developmental Changes in Adrenocorticotrophin (ACTH)-Induced Expression of ACTH Receptor and Steroid Acute Regulatory Protein mRNA in Ovine Fetal Adrenal Cells Reproductive Sciences, September 1, 2005; 12(6): 416 - 420. [Abstract] [PDF]

				J. R.G. Challis, S. G. Matthews, W. Gibb, and S. J. Lye Endocrine and Paracrine Regulation of Birth at Term and Preterm Endocr. Rev., October 1, 2000; 21(5): 514 - 550. [Abstract] [Full Text]

				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]