Conversion of progesterone to deoxycorticosterone in the human fetus: steroid 21-hydroxylase activity in fetal tissues

Steroid 21-hydroxylase activity was assayed in microsome-enriched fractions prepared from homogenates of a number of human fetal tissues. The activity of this enzyme was demonstrable in several tissues in addition to the adrenal, kidney, and gonads. The highest specific activities of the enzyme were found in adrenal, skin, kidney and urinary bladder. In addition, 21-hydroxylation of progesterone was demonstrated in microsome-enriched preparations of pancreas, thymus, spleen, testis and ovary. Thus a number of fetal tissues may contribute to the formation of deoxycorticosterone, which is present in high concentrations in plasma of the human fetus compared with those in men and nonpregnant women. Moreover, the potential for the in situ formation of DOC in presumed tissue sites of mineralocorticosteroid action was demonstrated.