Cortisol augments synthesis of growth hormone, but does not alter synthesis of prolactin and proopiomelanocortin, in the 120- to 125-day fetal ovine pituitary.

In adult animal pituitaries or in cultured pituitary tumor cells, glucocorticoids are regulators of GH, PRL, and proopiomelancortin (POMC) synthesis. However, ovine fetal plasma cortisol concentrations are low until shortly before parturition, suggesting that cortisol may not normally regulate hormone synthesis in the fetal pituitary. To investigate whether cortisol could affect fetal synthesis of GH, PRL, and POMC, we obtained fetal pituitary tissue from normal fetuses and from fetuses which had received cortisol infusion for 48 h. Tissues were labeled in short term organ culture and the newly synthesized proteins were displayed by two-dimensional gel electrophoresis and autoradiography. Results were quantified by computerized integration of the area and density of the autoradiographic spots after high resolution television scanning. Cortisol infusion augmented synthesis of GH in comparison to controls (P = 0.01), but did not alter PRL synthesis. Cortisol also did not inhibit POMC synthesis in either the anterior pituitary or the neurointermediate lobe. These data suggest that the pituitary-adrenocortical slow feedback inhibition of POMC synthesis is not functional in the ovine fetus at 120 to 125-days gestation, but that pituitary somatotropes are responsive to glucocorticoids at this stage of fetal development.