A comparison of adenosinetriphosphatase activity in testicular and ejaculated spermatozoa of the ram

ATPase activities in testicular and ejaculated spermatozoa from the same 4 rams have been compared under various conditions. The magnesium-activated and sodium-potassium-stimulated ATPase activity was found to be less in testicular than in ejaculated sper-matozoa despite the fact that the former cell type contained 50 % more protein than the latter. The pH optimum (pH 8.4) of the magnesium-dependent ATPase activity was the same for both types of spermatozoa. However, maximal stimulation of the enzyme by monovalent cations occurred at pH 8.1 in testicular and pH 6.7 in ejaculated spermatozoa and coincided approximately with optimal conditions for motility. Above pH 8.6 mono-valent cations inhibited rather than stimulated ATPase activities. The addition of increasing amounts of EDTA to the reaction mixtures greatly reduced the enzymic activity. In the presence of calcium ions, however, ATPase activities were sustained, but when the concentration of the added EDTA was increased to that of calcium the enzymic activity was significantly reduced; the resulting reduction in ATPase activity was ascribed to the chelating properties of EDTA. Determination of the enzyme and protein distribution in the head, mid-piece, tail, an