Montri ChulavatnatolMahidol University2018-10-122018-10-121982-01-01International Journal of Andrology. Vol.5, No.4 (1982), 425-43613652605010562632-s2.0-0019943348https://repository.li.mahidol.ac.th/handle/20.500.14594/30397Non‐motile spermatozoa freshly extruded from the rat caudal epididymis can be initiated to full motility immediately after diluting with 0.9% NaCl. The motility initiation was dependent on the pH, viscosity and osmolality of the diluent. Diluent with pH 4 to 8 could optimally initiate the motility. Osmolality of most diluents suitable for the initiation was between 130 to 600 mOsm/kg. The motility initiation was inhibited by Hg2+ > Cu2+ > Cd2+, chlorpromazine, Triton X‐100 and SDS. The following compounds showed essentially no inhibitory effect: EGTA, chlortetracycline, calcein, ruthenium red, phloridzin, myo‐inositol and carnitine. The findings suggested that spermatozoa were kept in quiescence in the cauda epididymis not by the pH, osmolality, viscosity, myo‐inositol, carnitine, Ca2+ or K+ of the caudal epididymal fluid. It was also suggested that motility initiation did not involve Ca2+. calmodulin and transport of Ca2+ or glucose across sperm membrane. Copyright © 1982, Wiley Blackwell. All rights reservedMahidol UniversityMedicineArticleSCOPUS10.1111/j.1365-2605.1982.tb00272.x