EFFECT OF HEAT-SHOCK ON FUNCTION OF FROZEN-THAWED BULL SPERMATOZOA

Deposition of spermatozoa in the reproductive tract of hyperthermic co ws could conceivably result in sperm damage. Accordingly, a series of experiments tested the effects of heat shock on functional characteris tics and free radical production of bull spermatozoa. Viability was re duced slightly by short-term (1 to 3 h) culture at 42 and 43 degrees C as compared with culture at 39 degrees C. There was no effect of cult ure at 42 degrees C on the ability of spermatozoa to undergo swim-up o r of 42 degrees C on the percentage of motile spermatozoa. However, ex posure to 41 degrees C for 3 h reduced percentage of motile sperm, 41 and 42 degrees C reduced sperm velocity and 43 degrees C decreased the proportion of spermatozoa undergoing swim-up. In other experiments, t here was no effect of heat shock (41 or 42 degrees C for 1 to 3 h) on DNA integrity, presence of intact acrosomes, or fertilizing ability of the spermatozoa. Superoxide production by spermatozoa was higher at 4 2 degrees C than at 39 or 41 degrees C, but there was no detectable hy drogen peroxide production at any temperature. The antioxidant, glutat hione, tended to improve the ability of spermatozoa to undergo swim-up at 39 degrees C but not at 43 degrees C. Taken together, these result s suggest that heat shock of a magnitude similar to that seen in vivo (41 to 42 degrees C) has little effect on sperm functions that affect fertilizing capability.