Pregnenolone radioactive

The substrate, pregnenolone (158 nmol) dissolved in propylene glycol, was added to the incubation flask containing the enzyme preparation and NAD in a final volume of 5 mL. After an incubation period of 60 minutes, the reaction was terminated by addition of 15 fiL of dichloromethane, and radioactive progesterone was added as a recovery standard. The organic phase was recovered, dried, and redissolved in 70% ethanol, and a sample was analyzed by HPLC. Figure 9.81 shows an analysis of an incubation mixture with and without incubation with the ovarian preparation. The substrate (not seen) is converted exclusively to progesterone. 

It has been shown that the fetal adrenal can convert progesterone and pregnenolone into cortisol in substantial yield (Sections 4.2.1 and 4.2.2), and, notably, Solomon (S25), after perfusion of fetuses with proges-terone-4- C, has isolated radioactive corticosterone and cortisol from the... 

By the action of a C20-C22 desmolaso, placental cholesterol has been found to be transformed to a very small extent into pregnenolone (Solomon et al., 1954 Solomon, 1960 Morrison et al., 1965). More recently, a significant conversion of cholesterol into pregnenolone (0.2-f).9% of the injected radioactivity) was obtained in human term placenta (Jaffe and Peterson, 1966). In the same study the concentration of total cholesterol was measured in the umbilical vein (mean value 74 mg/100 ml of plasma) and in the umbilical artery (mean value 88 mg/100 ml). On the other hand, the concentration of maternal total cholesterol was 196 mg/100 ml of plasma. Similar values of cholesterol have been found in umbilical vein blood by other authors (Itafstedt, 1955 Brody and Carlson, 1962 IJoyd, 1963 Mortinuir, 1964). 

After perfusion of anencephalic term fetuses with labeled pregnenolone, about 47% of the radioactive material in the perfusate was found as glucuroni de.s and 45 % as steroid cst er sulfates (A laeyuma et al., 1970). These values, wliich are in contrast to those in normal fetuses, could be explained by a sulfokinase deficiency in the anencephalic fetu.s as a consequence of the adrenal atrophy. 

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