Abstract
Aromatization of C-19-steroid (androstenedione;Δ4 A) and C-19 norsteroid (19- nortestosterone; NT) was measured in human placenta, liver and adipose tissues. The tissue homogenates (0.5-1.0 g w.w.) were incubated with [6, 7-31-1] -Δ4 or [6, 7-3H] -NT (10 μCi) and NADPH (1 mg/ml of 0.1M-bisodium phosphate buffer) at 37°C for 2 hr in air. The enzyme reaction was terminated with 3 volumes of ethyl acetate, and [4-14C] -estrone (El) and [4-14C] -estradiol-170 (E2) (10,000 dpm, 250μg) were added in the incubated sample. The extract with ethyl acetate was subjected to Bio-Rad AG1-X2 column chromatography. The phenol fraction thus obtained was subjected to thin layer chromatography (TLC) (cyclohexane-ethyl acetate = 2 : 1, V/V and chloroform-ethyl ether = 4 : 1, V/V). The resulting E1 and E2 were finally isolated by co-crystallization to constant specific activity and 3H/14C ratio of crystal crops.
In human placental microsomes, estrogen formation from Δ4A and NT was 8.10 and 1.84 pmol E1 + E2/hr/mg protein, respectively. In adult liver homogenates, only E1 (35-76 fmol/hr/g) was formed from Δ4 A, but E1 and E2 were formed (70 and 31 61 fmol/ hr/g, respectively) from NT. On the other hand, adipose tissue had the ability to aromatize Δ4A to E1 (38 - 69 fmol/hr/g), but its ability to aromatize NT was significantly lower than that for Δ4 A. These results show that NT is readily aromatized to estrogens in the liver.
