Roles for Potassium and Calcium Channels in the Initiation of Sperm Motility in Rainbow Trout

It is well known that the motility of spermatozoa in rainbow trout is suppressed by K+. We showed here that although trout sperm are completely immotile in medium containing 5 mM K+, motility was initiated by the subsequent addition of several mM Ca2+, suggesting that both K+and Ca2+are related to the process of the initiation of sperm motility. It was further found that K+channel blockers tetraethylammonium, nonyltriethylammonium, Ba2+and Cs+, as well as the Ca2+channel blocker verapamil, inhibited the initiation of sperm motility at doses at which these reagents inhibit chnnel‐related functions in other cells. However, Na+channel blocker, tetrodotoxin and anion channel blocker 4, 4‐diisothiocyatatostilbene‐2, 2′‐disulfonic acid inhibited the motility only at extremely high doses. These results suggest that transport of K+and Ca2+through ion channels at the plasma membrane of spermatozoa is the first event that triggers the initiation of sperm motility in rainbow trout.