Calretinin has been detected in various excitable cells but the presence and putative roles of such a calcium-binding protein has never been characterized in sperm.Epididymal spermatozoa were collected from C57Bl6 (wild-type, WT) or calretinin knockout (CR−/−) mice and Wistar rats. A specific staining for calretinin was detected by immunofluorescence in the principal piece of the...