ACTIVITY OF ASPARTATE-AMINOTRANSFERASE AND ACID-PHOSPHATASE IN CRYOPRESERVED TROUT SPERM

Milt of brown, rainbow and brook trout was cryopreserved. Activity of aspartate aminotransferase (AspAT) and acid phosphatase was assayed bo th in supernatants and in spermatozoa obtained from thawed sperm sampl es; additionally, post-thaw motility was evaluated. Enzyme activities differed according to fish species and were strongly affected by the t ype of cryoprotectant used. The activity in supernatants was usually h igher than that in spermatozoa because of protein leakage from injured cells. AspAT activity in cryopreserved spermatozoa correlated positiv ely with fertilization success in all three species. There was a negat ive correlation between activity of extracellular (supernatant) AspAT and fertilization rates in variants with dimethyl sulfoxide and dimeth ylacetamide-based extenders. The motility of thawed sperm, determined microscopically, provided some information on the cryopreservation eff iciency of trout milt.