Formation of estrogens by the pregnant mare. I. Metabolism of 7-3H-dehydroisoandrosterone and 4-14C-androstenedione injected into the umbilical vein.

Abstract

A mixture of 7-3H-dehydroisoandrosterone and 4-14C-androstenedione was injected into the umbilical vein of a pregnant mare. The abdomen was closed and urine collected for 4 days. The mare aborted a dead fetus 2 days after the operation. Steroid conjugates present in the maternal urine were hydrolyzed and separated into neutral and phenolic fractions. A total of 66% of the injected 3H and 58% of the 14C was present in the phenolic sulfate fraction. From this fraction estrone, 17α-estradiol, 17β-estradiol, equilin, equilenin, 17α-dihydroequilin and 17α-dihydroequilenin were isolated. Only estrone, 17α-estradiol and 17β-estradiol were radioactive and contained both 3H and 14C, while the ring B unsaturated estrogens were devoid of radioactivity. The conversion of injected 3Hdehydroisoandrosterone and 14C-androstenedione to estrone was 30 and 14%, respectively. These results indicate that ring B unsaturated estrogens are not formed from precursors used for the biosynthesis of the classic estrogens and probably...