Direct Evidence That Cyclic AMP is an Indispensable Factor for Initiation of Sperm Motility in Salmonid Fishes

Abstract

Although much information has been accumulated concerning the mechanism of sperm motility, the initiation mechanism of sperm motility has been remained unclear. Recently we have demonstrated that sperm motility of salmonid fishes such as chum salmon, rainbow trout, masu salmon and char is suppressed in the sperm duct by potassium (1,2) which is contained at higher concentrations in the seminal plasma (3). In the rainbow trout, during natural spawning, release of suppression by potassium in fresh water induces intraflagellar cyclic AMP and the endogenous cAMP to convert the axoneme from immotile state to motile one, thereby allowing axonemal movement i.e. sperm motility to occur (4,5). Here we show that cAMP is also the internal factor indispensable for initiation of sperm motility in another salmonid fish, chum salmon. We further discuss the possibility that cAMP is the general factor initiating sperm motility in other animals.