In the first series of experiments, the ability of cultured adrenal cells from 113-day-old ovine fetuses to produce both cAMP and corticosteroids in response to ACTH-(1-24) or to fetal (FPE) or newborn acidic pituitary extracts (NPE) was investigated daily. Basal cAMP output did not change during the culture period. When cells from 124-day-old ovine fetuses, or from 5-day-old lambs, were repeatedly stimulated (2 h/day for 4 days) by ACTH-(1-24) or by pituitary extracts, the cAMP responses increased with the same pattern. Outputs on day 4 were 7-fold higher than those on day 1 for ACTH-(1-24)-matured cells or for cells matured by FPE or NPE. The steroid output induced by ACTH-(1-24) or by FPE or NPE developed identically during the experiment to become, on day 4, more than 40-fold higher than on day 1. The response to ACTH-(1-24) on day 5 was also identical both in cAMP and corticosteroids whether the cells had been previously treated with ACTH-(1-24) or with FPE or NPE, In the second set of experiments, adrenal cells from 124-day-old-ovine fetuses either intact of hypophysectomized (Hx) at 118 days of gestation were cultured for 6 days in the absence or presence of ACTH-(1-24). ACTH-(1-24) treatment resulted in a development of cAMP and corticosteroid responses to the hormone which was slower for cells from Hx than cells from control fetuses during the first 3 days of culture. Likewise both cAMP and corticosteroids responses to ACTH-(1-24) of adrenal cells from Hx fetuses cultured for 1 to 3 days in the absence of ACTH were lower than those of cells from control fetuses cultured under the same conditions. These results demonstrate that the pituitary from 124-day-old ovine fetuses contains trophic (and steroidogenic) substances in a sufficient amount to allow in vitro adrenal maturation. Moreover, it appears that high mol wt forms of ACTH, which are most probably extracted by the method we used, did not prevent the in vitro development of the response to ACTH-(1-24). Finally, they show that removal of pituitary hormones in vivo resulted in a decreased potency of fetal adrenal cells to respond in vitro to ACTH-(1-24).
