THE INTERCONVERSION OF ESTRONE AND ESTRADIOLIN THE PERFUSED HUMAN PLACENTA12

Abstract

The interconversion of C14 labeled estrone and estradiol was studied in the perfused human placenta. The perfusate and the placenta were analyzed for radioactive estrogens after placentas were perfused for 35 minutes and for 4 hours. Reproducible ratios of estrone to estradiol were seen in the perfusate. They were independent of which precursor was used and, within the limits studied, of the amount of precursor and the weight of the perfused tissue. The estrone to estradiol ratios in perfusate and placenta changed with prolonged perfusion. The ratios in the perfusate differed from those in the placenta at 35 minutes and at 4 hours. After being perfused through the placenta for 2 cycles, the perfusate gained the capacity to interconvert estrone and estradiol. There was no detectable conversion of estradiol or estrone to estriol.