cortisol cortisone potency
Metabolism of cortisol and cortisone in the baboon fetus at midgestation. 1988
The metabolism of cortisol (F) and cortisone (E) in the fetal circulation is likely to influence the availability/biological potency of these corticosteroids and hence maturation of fetal organ systems. Therefore, we determined the MCR, production, peripheral interconversion, and placental extraction of F and E in the baboon fetus at midgestation. Radiolabeled F and E were infused into a femoral vein of fetuses (n = 7; 4 female, 3 male) exteriorized on day 100 of gestation (term = day 184). The MCR of F in the fetus (5.6 +/- 0.8 1/day) was lower (P less than 0.01) than that of E (13.1 +/- 2.2 1/day). Placental extraction of F (72.8 +/- 5.3%) and E (87.8 +/- 2.4%) were extensive indicating that the placenta contributes to fetal F/E MCR. Although the serum concentration (micrograms per dl) of F (20 +/- 2) exceeded (P less than 0.01) that of E (12 +/- 1), the calculated production rate (milligrams per day) of F (1.09 +/- 0.12) was not significantly different from that of E (1.55 +/- 0.27). The transfer constant for fetal conversion of F to E (29.0 +/- 6.0%) exceeded (P less than 0.01) that for reduction of E to F (1.8 +/- 0.4%). Therefore, the proportion of total F production derived from circulating E was only 2.2%, whereas the proportion of E derived from circulating F was 26.7%. These findings demonstrate that at midgestation the baboon fetus has minimal capacity for peripheral conversion of biologically inactive E to biologically active F, whereas the reverse conversion (F to E) is substantial.
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