Factors Influencing Metabolic Activity of Bull Spermatozoa. IV. pH, Osmotic Pressure, and the Cations, Sodium, Potassium, and Calcium

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Abstract
SUMMARY The combined effects of increasing pH from 4 to 8, of increasing potassium con- centration, at the expense of sodium, and of varying osmotic pressure on the aerobic metabolic responses of washed bovine spermatozoa provided with fructose have been determined in one experiment. Low pI4 and high potassium levels were found to be inhibitory of all measures of metabolism (oxygen uptake, fructose utilization, and lactic acid accumulation). Osmotic pressure had no significant effect. In a second e~:periment, variations in the calcium level of the diluent replaced the variations in the osmotic pressure. The inhibitory effect of potassium was eliminated by the presence of calcium. Consequently, ptI was the only variable affecting metabolic response. The uptake of fructose in the first few minutes after resuspension of the washed cells in a fructose-containing diluent is more rapid if the diluent has a pH of 5 than if it has a pH of 7.5, though on continued exposure the utilization ceases at the low pH but continues unabated at the higher one. Optimum preservation of the fertility function of spermatozoa after ejacu- lation is dependent upon reduction of their metabolic activity to minimum levels during storage and complete reversal of the inhibitory processes at insemination. Temperature control has been the inhibitory method of choice, with the diluent designed to provide protection against cold, and at body temperature to provide optimum conditions for motility and metabolic activity (4). These techniques have provided the basic advances responsible for the development of commercial artificial insemination of cattle since the discovery by Phillips (12) of the value of hens '-egg yolk for these purposes in 1939. However, observations made in a number of laboratories in the course of studies on the epididymis and in measurements of metabolic activity of sperma- tozoa have indicated that other means of metabolic control were possible. These include the finding of a metabolic regulator in epididymal spermatozoa (9), of a metabolic inhibitor ill ejaculated semen closely associated with the spermatozoa (2), and of the effects on metabolism of pH (10, 16), osmotic pressure (17), of the concentration of the cations, calcium and potassium (10, 22), the concen- tration of anions (3, 17), and of the partial pressure of carbon dioxide (18, 19). Ill addition, new evidence on the environment afforded spermatozoa in the epididymis, where they are normally quiescent, shows that the fluids are higher in potassium, lower in sodium and in calcium concentration than seminal plasma (7, 15).