The in vitro metabolism of estrone and estradiol-17β and their 3-sulfates by the renal tissues from pregnant and female fetal guinea-pigs

Abstract

High levels of estrone and estradiol-17β sulfates have been observed in the plasma of mother- and fetal guinea-pigs (albino variety). As the ability of fetal and maternal liver to synthesize estrogen sulfates is weak, we have studied the metabolism of [ 3H]-estrone; [ 3H]-estradiol-17β and their 3-sulfates in maternal and fetal kidneys, which are well-known in other species, to conjugated steroids. The synthesis of [ 35S]-estrogen sulfates was obtained after incubating 900 g supernatants from maternal and fetal kidneys, with [ 35S]-PAPS and estrogens. Incubations with different cellular fractions have shown that the renal tissue from the fetus have a higher soluble sulfotransferase activity than those from the mother. After incubation with [ 3H]-estrone and [ 3H]-estradiol-17β, 85% of the radioactivity was recovered in the sulfate fraction with fetal kidney, but only 8% with maternal kidney. Sulfatase activity, i.e. hydrolysis of [ 3H]-estrogen sulfates, has been found to be very low in both maternal and fetal microsome kidneys. It may be postulated that fetal kidney is the source of circulating estrogen sulfates as well as placenta in guinea-pigs.