Progesterone attenuates the inhibitory effects of cardiotonic digitalis on pregnenolone production in rat luteal cells

Abstract

Previous studies have shown that digoxin decreases testosterone secretion in testicular interstitial cells. However, the effect of digoxin on progesterone secretion in luteal cells is unclear. Progesterone is known as an endogenous digoxin-like hormone (EDLH). This study investigates how digitalis affected progesterone production and whether progesterone antagonized the effects of digitalis. Digoxin or digitoxin, but not ouabain, decreased the basal and human chorionic gonadotropin (hCG)-stimulated progesterone secretion as well as the activity of cytochrome P450 side chain cleavage enzyme (P450scc) in luteal cells. 8-Br-cAMP and forskolin did not affect the reduction. Neither the amount of P450scc, the amount of steroidogenic acute regulatory (StAR) protein, nor the activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) was affected by digoxin or digitoxin. Moreover, in testicular interstitial and luteal cells, progesterone partially attenuated the reduction of pregnenolone by digoxin or digitoxin and the progesterone antagonist, RU486, blocked this attenuation. These new findings indicated that (1) digoxin or digitoxin inhibited pregnenolone production by decreasing the activity of P450scc enzyme, but not Na(+)-K(+)-ATPase, resulting in a decrease on progesterone secretion in rat luteal cells, and (2) the inhibitory effect on pregnenolone production by digoxin or digitoxin was reversed partially by progesterone. In conclusion, digoxin or digitoxin decreased progesterone production via the inhibition of pregnenolone by decreasing P450scc activity. Progesterone, an EDLH, could antagonize the effects of digoxin or digitoxin in luteal cells.

Antisteroidogenic actions of hydrogen peroxide on rat leydig cells

“…Cells were primed with trilostane (4,5‐epoxy‐17‐hydroxy‐3‐oxoandrostane‐2‐carbonitrile, an inhibitor of 3β‐HSD, 10 −5 M) for 30 min and then incubated for 1 h with trilostane (10 −5 M) or trilostane plus 200 μM H 2 O 2 in the absence or presence of 25‐OH‐cholesterol (10 −5 M). At the end of incubation, the media were collected for pregnenolone RIA [Chen et al, 2002].…”

“…The concentrations of pregnenolone were determined by RIA as described previously [Chen et al, 2002; Chiao et al, 2002]. The sensitivity of the pregnenolone RIA was 16 pg per assay tube.…”

Differential effects of nonylphenol on testosterone secretion in rat Leydig cells

“…Western blotting method has been described elsewhere (Chen et al, 2002;Chiao et al, 2002;Tsai et al, 2003). Leydig cells (2 × 10 6 cells/tube) were incubated with or without NP at 0, 42.5 or 127.5 M in the presence or absence of hCG (0.05 IU/ml) for 1 h. After incubation, the cells were washed twice with ice-cold saline, and then the protein was extracted in 50 l of homogenization buffer (1.5% Na-lauroyl-sacrosine, 2.5 mM Tris base, 1 mM EDTA, and 0.1% PMSF, pH 7.8).…”

Downregulation of progesterone biosynthesis in rat granulosa cells by adlay (Coix lachryma-jobi L. var. ma-yuen Stapf.) bran extracts

“…[24][25][26] The granulosa cells (2 Â 10 6 cells) were incubated with medium containing ABM-Bu (0, 100 mg/ml), ABM-Bu-G (0, 100 mg/ml) or hCG (0.5 IU/ml) for 2 h. At the end of incubation, cells were washed twice with ice-cold saline and detached by trypsinization (1.25 mg/ml). The cells were collected and extracted in homogenization buffer (pH 8.0) containing 1.5% Na-lauroylsarcosine, 1 Â 10 À3 M EDTA, 2.5 Â 10 À3 M Tris-base, 0.68% PMSF and 2% proteinase inhibitor cocktail, and then disrupted by ultrasonic sonicator in an icebath.…”