Effects of dexmedetomidine on the steroidogenesis of rat immature Leydig cells.

Dexmedetomidine (DEX), an imidazole compound, is an anesthetic drug used perioperatively. In the current study, we investigated the effects of DEX on androgen production in rat immature Leydig cells in vitro. Leydig cells isolated from pubertal Sprague Dawley rats were treated with various concentrations of DEX (0.015-1.5 µM) for 3 h and medium 5α-androstanediol and testosterone levels and the expression of Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Srd5a1 and Akr1c14 in Leydig cells were determined. At 0.015-1.5 μM, DEX concentration-dependently inhibited androgen secretion and downregulated Cyp17a1 and Srd5a1 mRNA levels. DEX equally blocked the LH- and cAMP-stimulated secretion of androgens. Using the steroid substrates, 22R-hydroxycholesterol (for cytochrome P450 cholesterol side chain cleavage), pregnenolone (for 3β-hydroxysteroid dehydrogenase 1), progesterone (for cytochrome P450 17α-hydroxylase/C17,C20-lyase), androstenedione (for 17β-hydroxysteroid dehydrogenase 3), testosterone (for steroid 5α-reductase 1), and dihydrotestosterone (for 3α-hydroxysteroid dehydrogenase), it was demonstrated that DEX inhibited 22R-hydroxycholesterol, pregnenolone, progesterone, and testosterone-mediated 5α-androstanediol formation at 1.5 μM. Further study demonstrated that DEX also directly inhibited rat testis cholesterol side chain cleavage, 3β-hydroxysteroid dehydrogenation, and 17α-hydroxylation at 1.5 μM. DEX induced ROS production and increased apoptosis rate in immature Leydig cells after 24-h treatment at ≥0.15 μM. In conclusion, DEX directly inhibits the activities of some steroidogenic enzymes and downregulates the expression of Cyp17a1 and Srd5a1, and increases ROS production, thus leading to lower production of androgens in immature Leydig cells.