Differential Effects of Synthetic Adrenocorticotropin1–24and α-Melanocyte-Stimulating Hormone on Adrenal Function in Human and Sheep Fetuses*

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Abstract
The effects of ACTH1–24 and αMSH on the secretion of cortisol (F) and progesterone (P4) by newborn lambs and dispersed adrenal cells from term sheep fetuses have been measured. The responses have been compared with those of isolated human fetal adrenal cells and of isolated adrenal cells from nonpregnant adult sheep. In newborn lambs, ACTH1–24 significantly raised plasma F and P4 to peak values at 60–75 min. αMSH also raised F but had no effect on plasma P4. In vitro, adrenal cells from term sheep fetuses secreted significant amounts of F and P4 in response to ACTH1–24, even when the peptide was added at a concentration of only 5 pg/ml. aMSH stimulated F, but the response decreased with increasing concentrations (5 to 5000 pg/ml) of the peptide added. Secretion of P4 was significantly enhanced only by the addition of 5 and 50 pg/ml exogenous aMSH. Human fetal adrenal cells produced F in response to ACTH1–24, αMSH, and PRL, but not to hCG. Only ACTH1–24 stimulated release of P4 from human fetal adrenal cells. Isolated adrenal cells from nonpregnant adult sheep secreted significant amounts of F and P4 in response to ACTH1–24, but αMSH had no significant effect on the production of either of these steroids. These results from two species show 1) trophic agents other than ACTH can influence adrenal function in the fetus and newborn and 2) the response to αMSH and PRL differs quantitatively from that to ACTH. Agents such as αMSH and PRL may be important to the adrenal response during fetal life.