Functional evidence for involvement of bumetanide-sensitive Na+K+2Cl− cotransport in the hepatoportal Na+ receptor of the Sprague–Dawley rat

To investigate mechanisms involved in hepatoportal Na + sensing, responses of hepatic afferent nerve activity (HANA) to intraportal hypertonic NaCl injection were measured before, and after, intraportal infusion of inhibitors of Na + transport systems. HANA increased in response to the intraportal injection of 0.75 M NaCl in a dose-dependent manner. The HANA response was not affected by amiloride or 4-acetamido-4′-isothiocyanato-stilbene-2,2′-disulfonic acid (SITS), but was suppressed in a dose-dependent manner by intraportal infusion of ouabain, furosemide, or bumetanide. These results indicate that the hepatoportal Na + receptor senses the Na + concentration via the bumetanide-sensitive Na + K + 2Cl − cotransporter.