Crosstalk in the non-classical signal transduction of testosterone and retinol in immature rat testes

Abstract

This study aimed to investigate the effects of the interaction between testosterone and retinol on the rapid responses of cultured Sertoli cells obtained from 10-day-old immature rat testes. Non-classical actions of testosterone and retinol were investigated, and the activities of L-type voltage-dependent calcium channels (L-VDCC) and voltage-dependent potassium channels (Kv) were determined by measuring 45Ca2+ influx in whole testis. Additionally, the effects of testosterone and retinol on these channels were studied in primary culture of Sertoli cells using the patch-clamp technique. 45Ca2+ influx was used to observe a dose–response curve on tissues treated with retinol and/or testosterone for 2 min (10−12, 10−9 and 10−6 M and 10−9 and 10−6 M), and a concentration of 10−6 M was selected to investigate the mechanism of action of testosterone and retinol on rapid responses. Participation of the L-VDCC and Kv channels was investigated using nifedipine and tetraethylammonium chloride (TEA) inhibitors, respectively. Both, testosterone and retinol act through non-classical mechanisms, stimulating 45Ca2+ influx in immature rat testes. The response to testosterone was abolished by nifedipine and TEA, whereas the effects of retinol were partially blocked by nifedipine and completely inhibited by TEA. Retinol amplified the testosterone-induced effect on 45Ca2+ influx in the testes, suggesting a crosstalk between rapid responses (calcium influx) and cell repolarization via activation of Kv channels. Whole-cell electrophysiology data demonstrated that testosterone and retinol increased voltage-dependent potassium currents (Kv) in Sertoli cells; inhibition of these responses by TEA confirmed the involvement of TEA-sensitive K+ channels in these effects. Taken together, we demonstrate, for the first time, crosstalk between testosterone and retinol that is mediated by a non-classical mechanism involving the L-VDCC-triggered cell depolarization and activation of repolarization by Kv currents in Sertoli cells. These ionic modulations play a physiological role in Sertoli cells and male fertility via stimulation of secretory activities.