The structural specificity of carbohydrate in the initiation of rat sperm motility

Mammalian spermatozoa are stored in the cauda epididymis (CE) in a quiescent state and become motile when diluted with seminal plasma upon ejaculation. The structural specificity of a variety of sugars and sugar derivatives as diluents that are capable of initiating a transition of CE spermatozoa from the quiescent to the actively motile state was examined. It was found that monosaccharides, except those containing less than five-carbon skeletons, were good motility initiators; a trisaccharide tested showed reduced activity. The initiation activity was also independent of the structural stereospecificity and the nutritional value of the sugar. Based on these observations, a mechanism involving a receptor which handles sugar transport or sugar recognition in a transport process is proposed to be responsible for generating a signal that triggers CE spermatozoal motility.