Post-transcriptional action of ACTH in the control of P450c17 expression in rabbit adrenal glands.

Stimulation of transcription of the CYP17 gene by ACTH has been demonstrated previously by others using cultures of adrenal tissue from several species. In the present investigations we have demonstrated from measurements in pooled rabbit adrenal glands that after 4 or 6 days of ACTH injections no difference in amounts of CYP17 mRNA per microgram of total adrenal RNA was observed between ACTH and control animals. While the total amount of CYP17 mRNA per adrenal increased 1.4- to 1.7-fold over the injected and non-injected controls due to an increase in total RNA in the ACTH-stimulated adrenals, Western analysis of adrenal microsomal protein demonstrated that the amount of adrenal P450c17 protein, the product of the CYP17 gene, increased over 50-fold. The data show that ACTH is acting at both transcriptional and post-transcriptional loci to increase the amount of rabbit adrenal P450c17 and that the greater effect is post-transcriptional.