Cytochemical localization of ouabain-sensitive, K-dependent p-nitrophenylphosphatase in the rat hepatocyte.

To determine the localization of Na-K-ATPase activity in the rat hepatocyte, ouabain-sensitive, K-dependent p-nitrophenylphosphatase activity was studied cytochemically with a newly developed one-step lead citrate method devised by Mayahara et al. (1980). The liver was fixed with a mixture of 0.125% glutaraldehyde and 2% paraformaldehyde buffered with 30mM NaOH-PIPES instead of conventionally used 0.1M sodium cacodylate. Reaction products were localized predominantly on the sinusoidal and lateral membranes of the rat hepatocyte, which were remarkably abolished by addition of 10mM ouabain or by the deletion of K. They were localized on the cytoplasmic side of the membranes. Occasionally, reaction products were seen on the bile canalicular membrane, which were insensitive to ouabain and independent of K. These findings indicate that Na-K-ATPase is localized to the sinusoidal and lateral (basolateral) membranes of rat hepatocytes.