Figure 3.

Effect of cortisol upon steroidogenic enzyme activities in human adrenal cells. Representative TLC and quantification of specific metabolic products of [³H]-pregnenolone (A) or [³H]-DHEA (B) in cells exposed to cortisol (500 μm), expressed as the percentage of total radiolabeled steroids. Media were collected 6 h after adding [³H]-pregnenolone or 2.5 h after adding [³H]-DHEA. In both panels, tables display the ratios of product to precursor steroids and the corresponding changes in enzyme activities. Using either steroid precursor, cortisol markedly inhibited 3βHSD2 activity. C, 3βHSD2 activity, calculated from the ratio of secreted unlabeled androstenedione to unlabeled DHEA, measured by tandem mass spectrometry. 3βHSD2 activity showed dose-dependent inhibition at cortisol concentrations ≥10 μm. 17αOHPreg, 17αOH-pregnenolone; Preg, pregnenolone; 17αOHProg, 17αOH-progesterone; Prog, progesterone; DHEA, dehydroepiandrosterone; A’dione, androstenedione. *, P < 0.01; **, P < 0.001.