Deoxycorticosterone Sulfate Biosynthesis in Human Fetal Kidney*

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Abstract
The levels of deoxycorticosterone (DOC) and DOC-SO4 are extraordinarily high in umbilical cord plasma of human newborns compared to those in plasma of men and nonpregnant women. Progesterone is converted to DOC in minces, homogenates, and microsome-enriched preparations of human fetal kidney tissue. Since DOC, a mineralocorticosteroid, is formed in situ in kidney, its potential site of action, we sought to define whether sulfurylation of DOC also occurred in fetal kidney. We found that radiolabeled DOC-SO4 was formed from [3H]DOC and from [3H]progesterone in minces of human fetal kidneys. C-21 hydroxysteroid sulfotransferase activity was found to be localized principally in the cytosolic fraction of homogenates of human fetal kidney tissue and was present in both the cortical and medullary portions of fetal kidney. In cytosolic fractions prepared from homogenates of human fetal kidneys, we found that the apparent Km of the C-21 hydroxysteroid sulfotransferase for DOC was 4.7 µM; the reaction was linear with time for 60 min and was linear with protein concentration up to 1.2 mg × ml−1 incubation mixture. Thus, DOC-SO4, as well as DOC, is synthesized in the kidney of the human fetus, and kidney may be an important site of formation of these steroids that are found in fetal blood in very high concentrations.

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