Biphasic regulation by N6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP) of steroid 21-hydroxylase activity in rat hepatocytes.
Steroid 21-hydroxylase activity has been identified in many tissues, including liver. But it is possible that the enzyme found in the liver is different from adrenal 21-hydroxylase. In the adrenal cortex, steroid 21-hydroxylase activity is increased by corticotropin (ACTH); the effect of ACTH is mediated by cyclic AMP (cAMP), and presumably involves a cAMP-dependent protein kinase (PKA). It is not yet clear, however, how extra-adrenal steroid 21-hydroxylase activity is regulated. In the present study, we examined the effect of N6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP), forskolin, N-[2-(methylamino)ethyl]5-isoquinolinesulfonamide (H-8) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on steroid 21-hydroxylase activity in primary cultures of rat hepatocytes to determine the nature of regulation of extra-adrenal steroid 21-hydroxylase activity. Steroid 21-hydroxylase activity in hepatocytes incubated with 10(-11) M dbcAMP for 24 h was 1.6 times higher than that in control hepatocytes untreated with dbcAMP. On the other hand, steroid 21-hydroxylase activity decreased by 20 and 50% when the cells were incubated with 10(-5) and 10(-3) M dbcAMP, respectively. The stimulatory effect of 10(-11) M dbcAMP was not blocked by 10(-5) M H-8 (PKA inhibitor), but the inhibitory effect of 10(-5) or 10(-3) M cAMP was. TPA did not alter the activity of steroid 21-hydroxylase. These findings indicate that the steroid 21-hydroxylase in rat liver is regulated by mechanisms different from those in the adrenal glands.
Nasuda
K
K
Department of Pediatrics, Hamamatsu University School of Medicine, Shizuoka, Japan.
Endoh
A
A
Igarashi
Y
Y
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D013255:Steroid 21-Hydroxylase / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007546:Isoquinolines; D005576:Colforsin; D003994:Bucladesine; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D013255:Steroid 21-Hydroxylase; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate