The effects of heat on the metabolism and ultrastructure of ram testicular spermatozoa.

Abstract

Summary. The metabolism and ultrastructure of testicular spermatozoa have been examined after heating the testes of mature Merino rams to 40·5° C for 3 hr. The respiratory, glycolytic and synthetic activities of testicular spermatozoa collected between Days 1 and 5 after exposure to heat were depressed and remained low until observations ceased when sperm concentration fell. The internal structure of the cytoplasmic droplet of testicular spermatozoa collected after heating, in contrast to the complex system in control spermatozoa, contained numerous small and large vesicles with a hollow appearance. The remaining membranes of the droplet, as well as those of the mitochondria, assumed a flattened profile. A rise in incubation temperature from 34·5° C to 40·5° C increased the O2 uptake of control testicular spermatozoa by 65% and the utilization of glucose by 230%, suggesting that glucose is particularly important in the metabolism of testicular spermatozoa at high temperatures. The respiration of control washed ejaculated spermatozoa, but not that of control testicular spermatozoa, incubated in rete testis fluid collected after heating was 36% greater than in fluid collected before heating, possibly because of unidentified constituents not utilized in vivo by the reduced number of testicular spermatozoa and developing germinal cells.