Alterations of Na+,K+-ATPase activity after hypoxia and reoxygenation in the perfused rat liver: an electron microscopic cytochemical study

Background/Aims: Using the cerium technique for ultrastructural cytochemical studies, Na+,K+-ATPase activity was investigated in hypoxic and reoxygenated rat liver. Methods: In the control group, the livers were perfused with oxygenated hemoglobin-free Krebs-Henseleit buffer for 1 h. For hypoxia (60 min), the flow rate of the perfusate was decreased and oxygen was replaced by nitrogen. For reoxygenation, the liver was reperfused under oxygenated conditions for 5 min after 60 min of hypoxia. Results: In control livers, a strong Na+,K+-ATPase activity was detected at the basolateral membrane of hepatocytes while the apical membrane forming the bile canaliculi did not display any staining. In hypoxic livers, Na+,K+-ATPase activity had ceased in the plasma membrane of hepatocytes. In reoxygenated livers, Na+,K+-ATPase was rapidly reactivated in the basolateral hepatic membrane. The membrane of blebs generated during the hypoxic phase also showed enzyme activity. In addition, a striking accumulation of reaction product could be observed in about 10% of the apical membranes lining the bile canaliculi. Conclusion: The results indicate a plasticity of the Na+,K+-ATPase in hypoxic and reoxygenated rat liver.