HEPATORENAL BAROREFLEX IN CIRRHOTIC RATS

A hepatorenal baroreflex has been described in which increases in intrahepatic sinusoidal pressure stimulate an intrahepatic baroreceptor, resulting in increases in afferent hepatic (HNA) and efferent renal sympathetic nerve activity (RNA). Hepatic denervation prevents the increase in RNA. This baroreflex is postulated to contribute to the increase in RNA found in cirrhosis in which intrahepatic sinusoidal pressure is increased. However, the increased fibrosis in the cirrhotic liver may render the intrahepatic baroreceptor less sensitive to increases in intrahepatic sinusoidal pressure. By use of thoracic inferior vena caval constriction, intrahepatic sinusoidal pressure (i.e., inferior vena caval pressure, IVCP) was increased in control rats and rats with cirrhosis due to common bile duct ligation (CBDL) while HNA and RNA were measured. With increases in IVCP of 5 mmHg, increases in HNA (+38 +/- 2 and +44 +/- 3%) and RNA (+25 +/- 1 and +34 +/- 3%) were not different in control and CBDL rats, respectively. The slope gain, %Delta HNA/Delta IVCP, was +7.1 +/- 0.6 and +8.1 +/- 0.7%/mmHg in control and CBDL rats, respectively. Therefore the hepatorenal baroreflex is not desensitized in the CBDL rat, and the hepatorenal baroreflex is capable of contributing to the increase in RNA observed in cirrhosis.