[Basic characteristics of rat brain microsomal estradiol 2-hydroxylase].
The basic properties of estradiol 2-hydroxylase in rat brain microsomes were studied and compared to the known characteristics of rat liver microsomal estradiol 2-hydroxylase. Rat liver microsomal estradiol 2-hydroxylase, which has been considered to be a cytochrome P450-like enzyme, was largely inhibited by carbon monoxide. On the other hand, the effect of carbon monoxide on the activity of rat brain microsomal estradiol 2-hydroxylase was rather weak. A known inhibitor of cytochrome P450, SKF-525A inhibited rat liver microsomal estradiol 2-hydroxylase in a concentration-dependent manner. The concentration of SKF-525A causing 50% inhibition of liver microsomal estradiol 2-hydroxylase was 33 microM where the substrate concentration was 1 microM. Conversely, the inhibitory effect of SKF-525A on the activity of brain microsomal estradiol 2-hydroxylase was much less. Moreover, norepinephrine inhibited brain microsomal estradiol 2-hydroxylase in a competitive manner, however, the effect of physiological concentrations of norepinephrine on liver microsomal estradiol 2-hydroxylase was negligible. These results suggest that the nature of microsomal estradiol 2-hydroxylase in rat brain is quite different from that of liver microsomal estradiol 2-hydroxylase.
Tsukamoto
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Laboratory of Biochemistry, Faculty of Agriculture, Saga University, Japan.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002248:Carbon Monoxide / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology; D009638:Norepinephrine / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors
D065607:Cytochrome P-450 Enzyme Inhibitors; D011725:Pyridines; C013109:metapyrone; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D019363:Cytochrome P-450 CYP1A1; C020120:estrogen 2-hydroxylase; D009638:Norepinephrine