IMPLICATION THAT POTASSIUM FLUX AND INCREASE IN INTRACELLULAR CALCIUMARE NECESSARY FOR THE INITIATION OF SPERM MOTILITY IN SALMONID FISHES

Flux of K+ and changes in intracellular Ca2+ in the sperm of salmonid fishes were measured with spectrophotometry, ion electrode, microscopi c fluorometry, and radioisotope accumulation. Release of K+ occurred a t the initiation of sperm motility which is induced by decrease in ext ernal K+ and the K+ efflux and sperm motility were inhibited by K+ cha nnel blockers. Intracellular Ca2+ increased within a short period in K + free condition, and the accumulation of Ca-45 in sperm cells was hig her in motile sperm than that in immotile sperm. The efflux of K+ and the increase in intracellular Ca2+ were suppressed when external K+ co ncentration increased, i.e., sperm remained immotile. These results su ggest that efflux of K+ through K+ channel and subsequent increase in intracellular Ca2+ are prerequisite for the initiation of sperm motili ty. (C) 1994 Wiley-Liss, Inc.