Localization of various ATPases in fresh and cryopreserved bovine spermatozoa

Different ATPases may control the various functional changes that spermatozoa undergo just prior to fertilization, with the enzyme's specific location within the cell reflecting its function. The activities of Mg²⁺-ATPase, Ca²⁺Mg²⁺-ATPase, Na⁺K⁺-ATPase and Ca²⁺-ATPase were determined for head plasma membranes (HPM) and sperm body membrane (SBM) from both fresh (n = 4) and cryopreserved bovine spermatozoa (n = 4) and fresh homogenized whole spermatozoa (HWS) (n = 6). No activity of Ca²⁺Mg²⁺-ATPase was found in any preparation from spermatozoa. Ca²⁺-ATPase was detected in fresh SBM and HWS but not in HPM. Activity of Mg²⁺-ATPase and Na⁺K⁺-ATPase was higher in HPM than HWS or SBM (P < 0.01). Cryopeserving the whole sperm reduced the activities of all three enzymes, but Na⁺K⁺-ATPase was more sensitive to cryopreservation than Mg²⁺-ATPase (P ≤ 0.05). Enzyme location suggests that Ca²⁺-ATPase may be associated with events in the flagellum, while Mg²⁺-ATPase and Na⁺K⁺-ATPase may affect functions in the sperm head. Cryopreservation-induced damage to ATPases might be involved in reducing the fertilizing ability of cryopreserved spermatozoa.