Effect of Inhibition of δ 5,3β-Hydroxysteroid Dehydrogenase upon Pituitary and Serum Radioimmnoassayable Luteinizing Hormone in the Adult Male Rat

Abstract

Two synthetic steroid analogs (2α-cyano-4,-4,17α-trimethylandrost-5-en-17β-ol-3-one [cyano-ketone); 17β-hydroxy-4,4-17α-trimethl-androst-5-en-(2,3d)-isoxazole (isoxazole)] are potent selective inhibitors of 3β-hydroxysteroid dehydrogenase and of δ^5-4-3-ketosteroid isomerase (1). In the mature rat these analogs block adrenal glucorticoid synthesis and secretion. Adrenocortical, ovarian, and testicular interstitial cell hyperplasia are also demonstrable in these steroidogenic tissues after the administration of the inhibitors (2). Adrenocortical hyperplasia results from stimulation by adrenocorticotropic hormone secreted in response to the blockade in glucocorticoid synthesis produced by these analogs (3-5). In the present communication we report that the cyano-ketone increases pituitary and serum levels of radioimmunoassayable luteinizing hormone (LH) in the mature male rat, with a concomitant fall in plasma testosterone, suggesting that the interstitial cell hyperplasia produced by this compound may be secondary to increased gonadotropin secretion.

Materials and Methods. Adult male rats (13 weeks, 250 g, Charles River Breeding Laboratory, Wilmington, Mass.) received intramuscular injections of the cyano-ketone in dimethylsulfoxide or diluent alone. The cyano-ketone was administered at a dose of 10 mg/kg daily for 2 days and the animals were sacrificed by exsanguination 2 hr after the last injection (Table I) or for 8 days (days 1, 2, 3, 4, 7, 8, 9 and 10) and the animals were sacrificed 96 hr after the last injection (Table II). In another experiment the animals received the cyano-ketone at a dose of 60 mg/kg daily for 3 days with sacrifice 48 hr after the last injection (Table II). The adrenals and testes were flash-frozen at −80° and stored at −20°. The pituitaries were homogenized in 0.01 M sodium phosphate−0.15 M sodium chloride, pH 7.5, centrifuged (4°, 2000 rpm) and the supernatant was stored at −20°. Serum was stored at −20°.

3β-Hydroxysteroid dehydrogenase activity was determined in adrenal and testicular homogenates as previously described (6).