Mechanism of corticotropin and cAMP induction of mitochondrial cytochrome P450 system enzymes in adrenal cortex cells.
We studied the kinetics of corticotropin (ACTH) induction of mitochondrial cytochromes P450scc and P450c11 and their electron transport proteins, adrenodoxin and adrenodoxin reductase, in bovine adrenal cortex cells in primary culture. The mRNA levels of these enzymes increase and reach a peak within 3-12 h after ACTH addition. The protein levels of adrenodoxin reductase and P450scc show an increase only nearly 24 h after ACTH addition. After ACTH addition, the intracellular level of cAMP reaches maximal levels within 5 min, and then decreases gradually over 60 min. Hence, we examined the effect of a pulse of ACTH or cAMP analogs on enzyme and mRNA levels. Exposure of the cells to ACTH for 1-2 h was sufficient for maximal induction of the enzymes and P450scc mRNA. In contrast, the induction of the enzymes and the mRNA by cAMP analogs or forskolin required the continuous presence of these agents for over 12 h. But, these agents stimulated cortisol secretion to the medium quickly, indicating that they can activate some intracellular processes while not showing any effect on enzyme induction. The absence of any effect of prolonged cAMP pulses on enzyme and mRNA levels weakens the previous hypothesis that cAMP is the sole second messenger for the ACTH induction of steroidogenic enzymes in adrenal cortex cells. The inductive ability of a brief pulse of ACTH indicates that ACTH can rapidly initiate a series of reactions that result in enzyme induction many hours later.
Hanukoglu
I
I
Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel.
Feuchtwanger
R
R
Hanukoglu
A
A
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000302:Adrenal Cortex / Q000187:drug effects / Q000201:enzymology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000325:Adrenodoxin / Q000235:genetics; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004790:Enzyme Induction; D005287:Ferredoxin-NADP Reductase / Q000235:genetics; D005455:Fluorescent Antibody Technique; D007700:Kinetics; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
D012333:RNA, Messenger; D000325:Adrenodoxin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D000324:Adrenocorticotropic Hormone; D003577:Cytochrome P-450 Enzyme System; D000242:Cyclic AMP; D005287:Ferredoxin-NADP Reductase