Effects of exposing bovine sperm to bovine serum albumin, or freeze-thawing, on sperm-bound amidase activity.

Isolation of a self-selected population of motile spermatozoa is possible by using a gradient of bovine serum albumin (BSA). We determined if exposure to BSA altered the sperm or if isolated sperm differed from nonisolated cells in terms of motility or activity of sperm-bound amidase, either before or after subsequent cryopreservation. Exposure of sperm to 6% BSA in egg yolk Tris extender induced changes in the plasma and acrosomal membranes of sperm that resulted in exposure and activation of sperm-bound amidase (P less than .01). In experiment 2, semen extended in egg yolk Tris was cooled to 5 degrees C or layered onto a solution of 6% BSA in extender at 37 degrees C, from which the sperm that had swum into the BSA solution were recovered 2 h later and cooled to 5 degrees C. Sperm in both treatments were cryopreserved. The percentage of progressively motile sperm was determined visually and by track motility. Activity of sperm-bound amidase exposed to substrate was evaluated. After recovery of sperm from the 6% BSA solution, 81% were progressively motile as compared to 59% in the starting samples (P less than .01). However, the amount of exposed sperm-bound amidase also was greater (P less than .05); this was a deleterious change. Immediately after thawing, more (P less than .01) sperm were motile in samples of isolated sperm than for nonisolated cells (43 vs 24%), but after incubating the thawed sperm for 1 h at 37 degrees C there was no difference.(ABSTRACT TRUNCATED AT 250 WORDS)