ADRENERGIC-RECEPTORS ON CULTURED RAT EPIDIDYMAL CELLS - REGULATION OF CL- CONDUCTANCES

Adrenergic regulation of epididymal Cl- currents nas studied by the whole-cell patch-clamp technique using various alpha- and beta-receptor agonists and antagonists in primary cultured rat cauda epididymal cells. Cl- currents could be activated with varying frequency by noradrenaline (primarily alpha- and beta(1)-adrenoceptor-selective agonist, 1-5 mu M) isoprenaline (nonselective beta-adrenoceptor agonist, 5 mu M), salbutamol( beta(2)-adrenoceptor-selective agonist, 2 mu M), and phenylephrine (alpha(1)-adrenoceptor selective agonist, 1-2 mu M). Noradrenaline alone elicited Cl- current activation in 85% of the cells examined. In the presence of phentolamine (nonselective ol-adrenoceptor antagonist 15 mu M), noradrenaline elicited Cl- current activation in 63% of the cells examined, whereas noradrenaline-induced activation was observed in 33% of the cells examined in the presence of both atenolol and butoxamine (beta(1)- and beta(2)-adrenoceptor antagonists, respectively, 10 mu M). In 27% of single cells examined, a second current activation in response to salbutamol was observed after the first response to phenylephrine. When the order of stimuli was reversed, dual activation was also observed in 22% of the single cells examined, indicating the presence of both alpha- and beta-adrenoceptors in single epididymal cells. Profiles of time- and voltage-dependent Cl- current upon activation by different adrenoceptor agonists exhibited characteristics similar to those previously reported for Ca2+ and cAMP-activated Cl- currents, suggesting that regulation of epididymal Cl- conductances could be mediated by different adrenoceptor subtypes involving Ca2+ and cAMP as intracellular second messengers.