Ca2+-activated Cl- channel currents in rat ventral prostate epithelial cells

BACKGROUND. In many epithelial tissues, the Cl- efflux via Ca2+-activated Cl- channels (Cl-Ca) play a key role for the fluid secretion. To elucidate the mechanism of prostatic fluid secretion, the properties of whole-cell chloride conductance were investigated. MATERIALS AND METHODS. Rat prostate secretory epithelial cells (RPSECs) were isolated by collagenase treatment, and were used for the whole-cell voltage clamp. Both extra- and intracellular monovalent cations were replaced by N-methyl-D-glucamate to record the Cl- current selectively. RESULTS. A bath application of Ca2+-ionophore, ionomycin (0.2 muM), increased the membrane conductance with outwardly rectifying voltage-dependence. On step-like depolarization from -60 to +80 mV (500 msec), the ionomycin-induced current showed slowly activating kinetics, a known property of Cl-Ca current (I-Cl(Ca)) of other tissues. The relative permeability Of Cl-Ca to various anions was calculated from the reversal potentials measured under a total replacement of extracellular Cl- with various anions, and the relative order of permeability was SCN- > I- > Br- > Cl- much greater than gluconate. The amplitude Of I-Cl(Ca) was decreased by various anion channel blockers: niflumic acid (100 muM), DPC (100 muM), DIDS (I mM), and NPPB (200 muM). CONCLUSIONS. RPSECs have Cl-Ca that may provide Cl- efflux pathways for the exocrine secretions of the prostate. (C) 2003 Wiley-Liss. Inc.