Biosynthesis of estrogens in pregnant and non-pregnant guinea pigs

Guinea pig ovaries obtained from pregnant and non-pregnant animals, incubated in the presence of a NADPH-generating system, converted [3H]-dehydroepiandrosterone and [14C]testosterone to estradiol. Under the same conditions, no radioactive estrogen could be identified in adrenal and placental incubations. The rate of formation of estradiol from dehydroepiandrosterone was linear during the 30-min incubation. The initial rates of formation for estradiol were 415 X 10(-13) and 10.4 X 10(-13) mol/min/g tissue for the ovaries from pregnant and non-pregnant guinea pigs, respectively. The formation of estrone was shown only in the pregnant animal, and the initial rate of formation was 36.0 X 10(-13) mol/min/g tissue. These in vitro studies suggest that the major site of estrogen formation in both pregnant and non-pregnant guinea pigs is the ovary.