Hepatoportal bumetanide-sensitive K+-sensor mechanism controls urinary K+ excretion

To determine whether a K+-sensor mechanism exists in the hepatoportal regio n, periarterial hepatic afferent nerve activity responses to intraportal in jection of KCI were examined in anesthetized rats. Hepatic afferent nerve a ctivity increased in response to intraportal injection in a K+ concentratio n-dependent manner, and the increase was attenuated by inhibition of the Na +-K+-2Cl(-) cotransporter by bumetanide in a dose-dependent manner. These r esults suggest that a bumetanide-sensitive K+-sensor mechanism exists in th e hepatoportal region. Stimulation of this mechanism by intraportal KCl inf usion elicited an immediate and powerful kaliuresis with no significant cha nge in the plasma K+ concentration; this was significantly greater than the kaliuresis induced by intravenous KCl infusion and was attenuated by sever ing the periarterial hepatic nervous plexus. These results indicate that a hepatoportal bumetanide-sensitive K+-sensor mechanism senses the portal ven ous K+ concentration and that stimulation of this sensor mechanism causes k aliuresis, which is mainly mediated by the periarterial hepatic nervous ple xus.