Characterization of estrone hydroxylase activities in porcine endometrial cells.

The oxidation of estradiol to estrone in porcine endometrial cells is succeeded by hydroxylation at either 6 alpha- or 7 alpha-. The products are devoid of receptor affinity. Their formation is inhibited by cytochrome P450 blockers like ketoconazol but not by chloroquine and analogues. The hydroxylation at 6 alpha- proceeds with KM = 1.9 x 10(-7) M, that at 7 alpha- with KM = 3.6 x 10(-7) M. The respective values for the cytochrome P450-reductase cosubstrate NADPH are 1.7 x 10(-5) M and 1.9 x 10(-5) M. The kinetic parameters of the enzymes are compatible with a metabolic sequence: estradiol-->estrone--> 6 alpha/17 alpha-estrone.