Cryogenic preservation of fish and mammalian spermatozoa.

Various combinations of sucrose, reduced glutathione and potassium bicarbonate were tested for the cryogenic preservation of salmon spermatozoa. When a fast freezing procedure was followed, the extender that gave the best results was composed of 1 part of dimethyl sulphoxide (DMSO), as a protective agent, and 7 parts of a medium containing 125 mM-sucrose, 6.50 mM-reduced glutathione and 100 mM-potassium bicarbonate. Salmon and cod spermatozoa were kept frozen in this extender for 1 year. Freezing resulted in a reduction in the number of motile spermatozoa but had no significant effect on the degree of progression of motile spermatozoa or on their fertilizing capacity. When glycerol replaced DMSO in the extender and a slow freezing procedure was followed, similar results were obtained for the spermatozoa of bull or man; although the number of motile spermatozoa was reduced, there was no effect on the progressive motility score.