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.

The effect of pH on ram sperm collective motility driven by mitochondrial respiration

Ram sperm cells treated with 0.02 M 2-deoxy-D-glucose exhibit collective motility which is driven only by mitochondrial respiration. This motility was measured, by means of multichannel optical objective technique, under various [H+] concentrations (pH range 5.6-7.2) buffered by 0.125 M phosphate buffers. Semen was divided into 8 aliquots and motility was monitored simultaneously for intensity and duration within 10 min of ejaculation until its complete cessation. The optimal pH range found for the two above-mentioned parameters was in the range of 6.0-6.5. A certain characteristic of the pattern of sperm motility intensity (an oscillations phenomenon) was similarly related to pH. It is suggested that the mechanisms underlying the relationship between pH and motility are rather metabolic. Concerning the results, some practical implications are introduced.