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 Nat sensing, responses o f hepatic afferent nerve activity (HANA) to intraportal hypertonic NaCl inj ection were measured before, and after, intraportal infusion of inhibitors of Nat transport systems. HANA increased in response to the intraportal inj ection 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'-disul fonic acid (SITS), but was suppressed in a dose-dependent manner by intrapo rtal infusion of ouabain, furosemide, or bumetanide. These results indicate that the hepatoportal Nai receptor senses the Na+ concentration via the bu metanide-sensitive Na(+)K(+)2Cl(-) cotransporter. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.