Effects of phenobarbital and rose bengal on the ATPases of plasma membranes of rat and rabbit liver.

The effects of drugs which change the bile-salt-independent fraction of bile flow on Na(+)K(a+) and Mg(2+) activated ATPases were studied in membrane fractions rich in bile canaliculi. The administration of phenobarbital caused no induction of these enzymes which could explain the increased bile flow observed in the rat. Rose bengal, in addition to its strong photoxidative inhibition of both ATPases, inhibits the Na(+)K(+) ATPase of rat and rabbit bile canaliculi in the absence of light. A closely related substance, uranine, inhibits neither bile flow nor Na(+)K(+)ATPase. Inhibition of this enzyme by rose bengal may therefore be responsible for the observed effects of this dye on bile flow independent of bile salts.