Liver plasma membrane enzyme activities following glutaraldehyde fixation.

The Wachstein-Meisel ATPase histochemical method has been previously used to demonstrate the ultrastructural localization of this enzyme in both whole liver and isolated plasma membranes following fixation in glutaraldehyde. In the present study biochemical assay, of liver plasma membrane enzymes following fixation in cold 2.5% glutaraldehyde showed that approximately 40% of Mg2+-ATPase, but only 4% of (Na+-K+)-ATPase activity remained in membranes from either control or ANIT-treated rats. In addition, 5'-nucleotidase activity was almost abolished by fixation. The present results indicate that the Wachstein-Meisel method, when applied to biliary canaliculi, can reliably be used to demonstrate the ultrastructural, histochemical localization of Mg2+-ATPase but not that of (NA+-K+)-ATPase. Furthermore, the method permits a valid comparison to be made of the relative Mg2+-ATPase activity in normal and chemically damaged biliary canaliculi.