CORTISOL PRODUCTION IN FETAL ADRENALS OF THE SILVER FOX

The present study was designed to examine cortisol production by the s ilver fox fetal adrenals and their response to ACTH at different perio ds of prenatal life. Serum levels of cortisol were determined on days 35, 40, 45 and 50 of gestation (term on day 52) in embryos of both sex es. Cortisol content in adrenal tissue homogenates and its in vitro ad renal production were also investigated at the same time points. Hormo nes were measured by RIA. The levels of cortisol changed slightly duri ng embryonic life. The adrenal content and the in vitro production of cortisol increased sharply and progressively (by 4-10 times from days 35 to 50 of gestation). The rises in cortisol content and in vitro pro duction were associated with a rapid growth of the fetal adrenals. The re were no sex differences in cortisol level and its adrenal content. ACTH (50 mIU per sample) increased the in vitro cortisol production by the adrenals in the two sexes on all the studied days (by 3-4 times o n day 35 and by 1.4-1.7 times on day 50). These results indicate that 1) silver fox fetal adrenals are capable of synthesising cortisol; 2) ACTH is a potent activator of the in vitro cortisol production during embryonic life in this species. (C) 1997 by Elsevier Science Inc.