Endocrinology, Vol 124, 84-89, Copyright © 1989 by Endocrine Society

ARTICLES

Regulation of growth hormone (GH) secretion by GH-releasing factor, somatostatin, and insulin-like growth factor I in ovine fetal and neonatal pituitary cells in vitro

BL Silverman, M Bettendorf, SL Kaplan, MM Grumbach and WL Miller
Department of Pediatrics, University of California, San Francisco 94143.

Serum GH concentrations in the ovine fetus are much higher than those in the neonate, and the maximal GH response induced by GRF is 5-fold greater in the fetus than in the neonate. To clarify these in vivo observations further, we studied the effects of GRF, somatostatin (SRIF), and insulin-like growth factor I (IGF-I) on primary cultures of fetal and neonatal ovine pituitary cells. GH secretion from fetal ovine pituitary cells increased from 148 +/- 34 to 950 +/- 130 ng/10(5) cells.3 h in response to 1 nM GRF, whereas GH secretion from neonatal pituitary cells rose from 113 +/- 26 to 1221 +/- 129 ng/10(5) cells.3 h, a significantly greater response (P less than 0.001). This greater GRF-induced GH response in neonatal than fetal cells differs from the response in vivo and suggests that the increased in vivo response in the fetus is not due to inherently increased sensitivity of pituitary cells to GRF. SRIF (10 nM) decreased maximal GRF-induced GH secretion by 37 +/- 3% in fetal cells compared with 59 +/- 8% in neonatal cells (P less than 0.01). This may explain in part the decreased in vivo sensitivity to SRIF in the ovine fetus compared to that in the neonatal lamb. In fetal pituitary cells, 10 nM GRF increased ovine (o) GH mRNA from 100 +/- 14% to 145 +/- 40%, SRIF decreased oGH mRNA to 84 +/- 3%, and GRF and SRIF in combination increased fetal oGH mRNA to 126 +/- 24%. Values in neonatal pituitary cell cultures were similar (control, 100 +/- 17%; GRF, 132 +/- 6%, SRIF, 85 +/- 15%; GRF plus SRIF, 105 +/- 26%). Pretreating fetal cells with 100 nM IGF-I for 3 days reduced GRF- stimulated GH secretion from 1049 +/- 38 to 232 +/- 8 ng/10(5) cells.3 h (P less than 0.001). Similarly, IGF-I pretreatment of neonatal cells reduced GRF-stimulated GH secretion from 810 +/- 18 to 419 +/- 16 ng/10(5) cells.3 h (P less than 0.001). The mean secreted IGF-I was 0.58 U/ml (36 nM) in culture medium from neonatal cells and was unchanged by incubation for 3 days with 5 micrograms/ml hGH. Secreted IGF-I in medium from fetal cells was 0.87 U/ml (54 nM) without GH and 0.81 U/ml (51 nM) after incubation with human GH. IGF-I mRNA was present in neonatal pituitary and brain.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				K Katoh, G Furukawa, K Kitade, N Katsumata, Y Kobayashi, and Y Obara Postprandial changes in plasma GH and insulin concentrations, and responses to stimulation with GH-releasing hormone (GHRH) and GHRP-6 in calves around weaning J. Endocrinol., December 1, 2004; 183(3): 497 - 505. [Abstract] [Full Text] [PDF]

				N. R. Cox, N. E. Morrison, J. L. Sartin, F. C. Buonomo, B. Steele, and H. J. Baker Alterations in the Growth Hormone/Insulin-Like Growth Factor I Pathways in Feline GM1 Gangliosidosis Endocrinology, December 1, 1999; 140(12): 5698 - 5704. [Abstract] [Full Text]

				D. K. Reed, A. I. Korytko, R. W. Hipkin, W. B. Wehrenberg, A. Schonbrunn, and L. Cuttler Pituitary Somatostatin Receptor (sst)1-5 Expression during Rat Development: Age-Dependent Expression of sst2 Endocrinology, October 1, 1999; 140(10): 4739 - 4744. [Abstract] [Full Text]

				P Pirazzoli, E Cacciari, R De Iasio, M C Pittalis, P Dallacasa, S Zucchini, S Gualandi, S Salardi, C David, and S Boschi Developmental pattern of fetal growth hormone, insulin-like growth factor I, growth hormone binding protein and insulin-like growth factor binding protein-3 Arch. Dis. Child. Fetal Neonatal Ed., September 1, 1997; 77(2): 100F - 104. [Abstract] [Full Text]