The Changing Response Pattern of Sheep Fetal Adrenal Cells throughout the Course of Gestation*

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Abstract
The output of cortisol and progesterone by adrenal cells isolated from sheep fetuses on days 50, 100, and 130 of pregnancy and at term has been measured after the addition of ACTH-(l-24), αMSH, combinations of the peptides, or pituitary cells from fetuses of the same age. ACTH-(l-24) stimulated cortisol output from fetal adrenal cells on day 50 and 130 and term but not on day 100. The ED50 for cortisol output was greater at day 50 than at day 130 or term, although the stimulation ratio was similar on day 50 and at term. Progesterone output by fetal adrenal cells was stimulated by ACTH at all ages studied. The ED50 for progesterone output was greater on day 50 than at later times in pregnancy. Coincubation of fetal adrenal cells with pituitary cells from fetuses of the same age gave results essentially similar to those obtained with ACTH with respect to the capacity to stimulate cortisol and progesterone output. aMSH stimulated cortisol output, but only at term, and partially antagonized the stimulatory effect of ACTH at that time. Fetal pituitary cells were also incubated with maternal sheep adrenal cells, and they stimulated cortisol output at all ages studied. We conclude that 1) fetal pituitary cells contain potential trophic agents throughout the period from day 50 to term; 2) the sensitivity of sheep fetal adrenal cells to ACTH increases from day 50 of pregnancy, although the output of cortisol is reduced at midgestation (day 100), and 3) reemergence of the capacity for cortisol output by the fetal adrenal in late pregnancy may involve the activities of enzymes distal to progesterone synthesis. (Endocrinology106: 1371, 1980)