REGULATION OF BOVINE ADRENAL-CELL CORTICOTROPIN RECEPTOR MESSENGER-RNA LEVELS BY CORTICOTROPIN (ACTH) AND ANGIOTENSIN-II (A-II)

Bovine adrenal fasciculata-reticularis cells (BAC) expressed at least four ACTH receptor (ACTH-R) mRNA transcripts, one major of 3.6 kb and three minor of 4.2, 1.8 and 1.3 kb. ACTH and A-II increased ACTH-R mRN A levels in a time- and dose-dependent manner. At maximal concentratio ns, ACTH caused a 2.7-fold increase in the level of the major transcri pt of 3.6 kb with an ED(50) = 10(-11) M and A-II produced a 2.4-fold i ncrease with an ED(50) = 5 X 10(-8) M. Under our experimental conditio ns, the stimulatory effects of both hormones appeared to be due to pos t-transcriptional changes rather than to transcriptional regulation si nce the hormonal effects were also observed in actinomycin-treated cel ls. The results indicate that regulation of ACTH-R mRNA levels may be one mechanism by which ACTH and A-II regulate adrenocortical functions .