IN-VIVO EFFECTS OF ADRENOCORTICOTROPIN ON C-JUN, JUN-B, C-FOS AND FOS-B IN RAT ADRENAL

We have studied the in vivo effects of adrenocorticotropin (ACTH) on m RNA levels of c-jun, jun-B, c-fos and fos-B, in rat adrenals. In contr ol rats, c-jun mRNA was abundant in both zona glomerulosa (ZG) and zon a fasciculata-reticularis (ZF-R). Although less abundant than c-jun, t he mRNA of jun-B could be detected in both zones, whereas that of c-fo s could barely be detected and that of fos-B could not. After an injec tion with short acting ACTH, mRNA levels of c-jun, c-fos, jun-B and fo s-B were maximally increased in both zones within 30 min. Within 5h, t he mRNA levels decreased towards control levels for c-jun, to below co ntrol levels for jun-B, and to undetectable levels for c-fos and fos-B . After a sustained stimulation by two daily administrations of long a cting ACTH, the mRNA of c-jun was still abundant in both zones, althou gh its level decreased by 50% and 80% after 36h and 9 days, respective ly, after the first injection. Under such conditions, the mRNA level o f jun-B was increased, that of fos-B could barely be detected, and tha t of c-fos could not be detected. To conclude, these results suggest t hat jun-B, fos-B, and also c-fos play a role in triggering early event s leading to an increased steroidogenesis, as well as a basic role in maintaining the integrity of the adrenal cortex in the case of c-jun a nd jun-B.