K⁺ channel currents in rat ventral prostate epithelial cells

BACKGROUND. Electrophysiological function of the normal prostate has not been extensively studied. In particular, ion channel currents and their regulation have not been studied in freshly-isolated prostate cells. METHODS. Rat prostate secretory epithelial (RPSE) cells were isolated by collagenase treatment. Columnar epithelial cells were used for nystatin-perforated, whole-cell voltage clamp, and the intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured using fura-2. RESULTS. Step-like depolarizing pulses (900 msec) starting from - 90 mV induced out-wardly rectifying K⁺ currents without inactivation. ACh (10 μM) or ATP (100 μM) increased the outward current and hyperpolarized the cell membrane potential. Ionomycin (0.1 μM), a Ca²⁺ ionophore, induced a similar increase in the outward current. TEA (5 mM), charybdotoxin (50 nM), and iberiotoxin (30 nM) inhibited the effect of ACh (or ATP) on the outward current, whereas apamin (100 nM) had no effect. The [Ca²⁺]_i of RPSE cells was increased by ACh, ATP, and UTP. CONCLUSIONS. RPSE cells have iberiotoxin-sensitive Ca²⁺-activated K⁺ channels that may play an important role in the exocrine secretions of the prostate.