Effect of the membrane active ionophore, nigericin, on motility of ram spermatozoa.

Ram spermatozoa diluted in Ringer-fructose-phosphate to a concentration of 5 X 10(6) cells/ml, were exposed to continuous variations of pH, using HCl or NaOH. Percent of motility and ATP level were measured within 1-2 min from the pH change. High percent of motility was observed in the range of 2 pH units, between pH 6.5 to 8.5, regardless of the source of the ATP production: mitochondria, fructolysis, or both. In the presence of nigericin (H +/K+ exchanger), two peaks of high motility were observed: one at alkaline pH (7.8-8.3) and the other at acidic pH (6.5-7.0). When nigericin was added to cells inhibited by 2-deoxyglucose (possessing mainly mitochondrial motility), the high percent of motility was noted at the alkaline pH (7.2-7.6). However, when nigericin was added to cells inhibited by Antimycin-A (possessing mainly fructolytic motility), the high percent of motility was observed at the acid pH (6.0-6.7). The ATP level was correlated with the pattern of the motility.