Pharmacological profile of inhibition of the chloride channels activated by extracellular acid in cultured rat Sertoli cells

Sertoli cells from mammalian testis are key cells involved in the development and maintenance of stem cell spermatogonia as well as in the secretion of a Cl$^{-}$ and K$^{+}$-rich fluid into the lumen of seminiferous tubules. The pharmacology and contribution of Cl$^{-}$ channels to the physiology of Sertoli cells were investigated using whole-cell patch clamp and iodide efflux experiments applied to cultured rat Sertoli cells. We characterized an outwardly rectifying Cl$^{-}$ current stimulated by various acid species including the physiologically relevant lactic acid. Using the iodide efflux technique, the pharmacological properties of this Cl$^{-}$ current, noted ICl$_{\rm acid}$, revealed Ca$^{2+}$-independent inhibition by DIDS (IC$_{50}$ = 27 $micron$M), glibenclamide (IC$_{50}$ = 31 $micron$M) and DPC (IC$_{50}$ = 86 $micron$M). ICl$_{\rm acid}$ was neither affected by calix[4]arene nor by 9-AC. The order of potency for inhibition of ICl$_{\rm acid}$ is DIDS $\approx $ glibenclamide $>$ DPC $>\!>$ calix[4]arene, 9-AC. For comparison, the inhibitory profile of the swelling- and ATP-activated Cl$^{-}$ currents in Sertoli cells is DPC = DIDS $>\!>$ glibenclamide = 9-AC for ICl$_{\rm swell}$ and DPC = 9-AC = DIDS $>\!>$ glibenclamide for ICl$_{\rm ATP}$. This description provides new insights into the physiology and pharmacology of the endogenous Cl$^{-}$ channels expressed and potentially involved in fluid secretion in Sertoli cells