Intracellular alkalinization enhances inward rectifier K+ current in retinal horizontal cells of catfish.

Isolated cone-driven horizontal cells dissociated from catfish retina were voltage-clamped using the whole-cell patch-clamp technique. The effects of acidification and alkalinization on an anomalous type, inwardly-rectifying K+ current (IRK+) were investigated. The magnitude of IRK+ was enhanced by raising the intracellular pH above 7.4, however, in contrast, intracellular acidification had little effect on this current. The range over which intracellular pH ([pH]i) modulates IRK+ is different from that for modulation of a sustained high-voltage activated calcium current in these same cells and also for proton-sensitive, inward rectifier currents in starfish oocytes, skeletal muscle and heart myocytes.