			Home About us Contact

Hepatic Arterial Buffer Response (hepatic + arterial_buffer_response)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Hepatic arterial buffer response in patients with advanced cirrhosis

HEPATOLOGY, Issue 3 2002
Veit Gülberg
Hepatic arterial buffer response (HABR) is considered an important compensatory mechanism to maintain perfusion of the liver by hepatic arterial vasodilation on reduction of portal venous perfusion. HABR has been suggested to be impaired in patients with advanced cirrhosis. In patients with hepatopetal portal flow, placement of a transjugular intrahepatic portosystemic shunt (TIPS) reduces portal venous liver perfusion. Accordingly, patients with severe cirrhosis should have impaired HABR after TIPS implantation. Therefore, the aim of this study was to investigate the effect of TIPS on HABR as reflected by changes in resistance index (RI) of the hepatic artery. A total of 366 patients with cirrhosis (Child-Pugh class A, 106; class B, 168; class C, 92) underwent duplex Doppler ultrasonographic examination with determination of RI and maximal flow velocity in the portal vein before and 1 month after TIPS placement. Portosystemic pressure gradient was determined before and after TIPS placement. In 29 patients with hepatofugal portal blood flow, RI was significantly lower than in 337 patients with hepatopetal flow (0.63 ± 0.02 vs. 0.69 ± 0.01; P < .001). TIPS induced a significant decrease of the RI in patients with hepatopetal flow (RI, 0.69 ± 0.01 before vs. 0.64 ± 0.01 after TIPS; P = .001) but not in patients with hepatofugal flow (RI, 0.63 ± 0.02 before vs. 0.63 ± 0.02 after TIPS; NS). This response was not dependent on the Child-Pugh class. In conclusion, our results suggest that some degree of HABR is preserved even in patients with advanced cirrhosis with significant portal hypertension. [source]

Regulatory processes interacting to maintain hepatic blood flow constancy: Vascular compliance, hepatic arterial buffer response, hepatorenal reflex, liver regeneration, escape from vasoconstriction

HEPATOLOGY RESEARCH, Issue 11 2007
W. Wayne Lautt
Constancy of hepatic blood flow (HBF) is crucial for several homeostatic roles. The present conceptual review focuses on interrelated mechanisms that act to maintain a constant HBF per liver mass. The liver cannot directly control portal blood flow (PF); therefore, these mechanisms largely operate to compensate for PF changes. A reduction in PF leads to reduced intrahepatic distending pressure, resulting in the highly compliant hepatic vasculature passively expelling up to 50% of its blood volume, thus adding to venous return, cardiac output and HBF. Also activated immediately upon reduction of PF are the hepatic arterial buffer response and an HBF-dependent hepatorenal reflex. Adenosine is secreted at a constant rate into the small fluid space of Mall which surrounds the terminal branches of the hepatic arterioles, portal venules and sensory nerves. The concentration of adenosine is regulated by washout into the portal venules. Reduced PFreduces the washout and the accumulated adenosine causes dilation of the hepatic artery, thus buffering the PF change. Adenosine also activates hepatic sensory nerves to cause reflex renal fluid retention, thus increasing circulating blood volume and maintaining cardiac output and PF. If these mechanisms are not able to maintain total HBF, the hemodynamic imbalance results in hepatocyte proliferation, or apoptosis, by a shear stress/nitric oxide-dependent mechanism, to adjust total liver mass to match the blood supply. These mechanisms are specific to this unique vascular bed and provide an excellent example of multiple integrative regulation of a major homeostatic organ. [source]

A distinct nitric oxide and adenosine A1 receptor dependent hepatic artery vasodilatatory response in the CCl4 -cirrhotic liver

LIVER INTERNATIONAL, Issue 7 2010
Alexander Zipprich
Abstract Increase of portal venous vascular resistance is counteracted by decrease of hepatic arterial vascular resistance (hepatic arterial buffer response). This process is mediated by adenosine in normal livers. In cirrhosis, hepatic arterial vascular resistance is decreased but the involvement of adenosine in this process is unknown. The aim of our study was to identify the signalling pathway responsible for the decreased hepatic arterial resistance in cirrhotic livers. Methods: Cirrhosis was induced by CCl4. Using a bivascular liver perfusion dose,response curves to adenosine of the HA were performed in the presence and the absence of pan-adenosine blocker (8-SPT), A1 blocker (caffeine) or nitric oxide synthase-blocker (l -NMMA) after preconstriction with an ,1-agonist (methoxamine). Western blot of the HA were used to measure the density of the A1 and A2a receptors. Results: Adenosine caused a dose dependent relaxation of the hepatic artery of both cirrhotic and control animals that were blocked in both groups by 8-SPT (P<0.02). The response to adenosine was greater in cirrhotic rats (P=0.016). Both l -NMMA (P=0.003) and caffeine reduced the response to adenosine in cirrhotic but not in control animals. Western blot analysis showed a higher density of A1 and a lower density of A2a receptor in cirrhotic animals (P<0.05). Conclusion: The adenosine-induced vasodilatation of the HA is increased in cirrhotic rats suggesting a role for adenosine-NO in the decreased hepatic arterial vascular resistance found in cirrhosis. This significantly greater response in cirrhosis by the A1 receptor follows the same pathway that is seen in hypoxic conditions in extra-hepatic tissues. [source]