The Effects of Temperature, Osmolality and Hydrogen Ion Concentration on the Activation and Acrosome Reaction of Golden Hamster Spermatozoa

Summary. Golden hamster spermatozoa were incubated in a medium consisting of 50% Tyrode's solution and 50% γ-globulin-free human serum (gas phase, air). The effects of incubation temperatures of 42 to 16° C were studied. Sperm activation, acrosome reaction and survival were impaired at 42° C. Below 42° C, the time required for activation to occur was inversely proportional to the incubation temperature. Spermatozoa could be activated almost instantly by warming them to 37° C following preincubation for `critical' lengths of time at temperature of 31° C and below. The acrosome reaction reached a maximum level approximately 1½ hr after activation at 33 to 40° C. At 31 to 23° C, the time increased as lower temperatures were used. Following warming, the acrosome reaction reached its maximum about 3 hr after the critical time. The final percentages of activation and acrosome reaction and the survival rates were not affected between 25 and 40° C. The possibility that at least three phases or processes are involved in activation and acrosome reaction is discussed. Osmotic pressures ranging between 193 and 470 mosmol were tested with the best rates of sperm activation, acrosome reaction and survival occurring at 230 to 343 mosmol. The effects of pH values of 5·4 to 8·6 were tested. Activation, acrosome reaction and survival were best within the range of 7·2 to 7·8. The relationships of the observed pH and osmotic pressure optima to conditions within the female genital tract are considered.