Nongenomic effect of testosterone on chloride secretion in cultured rat efferent duct epithelia

Short-circuit current (Isc) technique was used to investigate the role of t estosterone in the regulation of chloride secretion in cultured rat efferen t duct epithelia. Among the steroids tested, only testosterone, and to a le sser extent, 5 alpha -dihydrotestosterone (5 alpha -DHT), reduced the basal and forskolin-induced Isc in cultured rat efferent duct epithelia when add ed to the apical bathing solution. Indomethacin, a 3 alpha -hydroxysteroid dehydrogenase, did not affect the inhibitory effect of 5 alpha -DHT. The ef fect of testosterone occurred within 10-20 s upon application and was dose dependent with apparent IC50 value of 1 muM. The effect was abolished by re moval of Cl- but not HCO3- from the normal Krebs-Henseleit solution, sugges ting that testosterone mainly inhibited Cl- secretion. The efferent duct wa s found to be most sensitive to testosterone, while the caput and the cauda epididymidis were only mildly sensitive. Cyproterone acetate, a steroidal antiandrogen, or flutamide, a nonsteroidal antiandrogen, did not block the effect of testosterone on the forskolin-induced Isc, nor did protein synthe sis inhibitors, cycloheximide, or actinomycin D. However, pertussis toxin, a G(i) protein inhibitor, attenuated the inhibition of forskolin-induced Is c by testosterone. Testosterone caused a dose-dependent inhibition of forsk olin-induced rise in cAMP in efferent duct cells. It is suggested that the rapid effect of testosterone was mediated through a membrane receptor that is negatively coupled to adenylate cyclase via G(i) protein. The role of no ngenomic action of testosterone in the regulation of electrolyte and fluid transport in the efferent duct is discussed.