Fine structural cytochemical localizations of phosphatase activities of rat and guinea pig

The fine structural localization of several phosphatase activities was studied in spermatozoa obtained from the caudae epididymides of mature rats and guinea pigs. Fresh sperm and sperm fixed in hydroxyadipaldehyde or glutaraldehyde were incubated in a substrate containing medium either at pH 7.0 using lead ions as the capture agent, or at pH 9.0 with cadmium ions. Activity sensitive to sulfhydryl reagents and glutaraldehyde fixation was evident on elements of the axial filament complex at pH 7.0 with ATP and activators, Mg²⁺ or Ca²⁺, and to a lesser extent with ADP and Mg²⁺ or ITP and Mg²⁺. At pH 9.0, reaction product was localized on the medial surface of the coarse fibers. This activity was obtained with ATP, activated by Ca²⁺, and was resistant to both sulfhydryl agents and glutaraldehyde fixation. Calcium dependent, mercurial-stimulated ATPase activity was also demonstrated at pH 9.0 on the plasma membrane of the head and the outer membrane of the acrosome vesicle in glutaraldehyde-fixed guinea pig sperm. Mitochondrial activity was demonstrated with several substrates, including ATP at both pH 7.0 and 9.0.