MORPHOLOGICAL-CHARACTERISTICS AND ATPASE ACTIVITY OF PERMEABILIZED EPIDIDYMAL BULL SPERMATOZOA

The treatment of bull spermatozoa from epididymal cauda with 5 mug dig itonin per mul cells led to the destruction of the plasma membrane whi ch was shown by electron microscopy. Structural changes of mitochondri a and of the axoneme were not found. The functional inactness was main tained. The plasma membranes of hypotonically treated spermatozoa were permeable for succinate and the mitochondria showed a diminished func tional intactness. For the total ATPase activity of digitonin-treated cells, mainly representing the dynein ATPase, a maximal activity of 20 ,3 nmol ATP x min-1 x mul cells-1 (mean +/- S. D.; n = 8) and an appar ent half saturation constant of 0,29 mM ATP were determined. The porti ons of Na+-K+-ATPase and mitochondrial ATPase in the total ATP-splitti ng activity were found to be less than 15 %. In comparison to the capa city of mitochondrial ATP production, the maximal activity of ATP cons uming reactions amounted to about 70 %. These results support findings that the ATP turnover of spermatozoa is more limited by the ATP consu mption than by the ATP production.