Hepatic artery buffer response following left portal vein ligation: its role in liver tissue homeostasis

Occlusion of a lobar portal vein is known to induce atrophy of downstream l iver lobes and hypertrophy of contra-lateral lobes. Changes in portal flow are known to be compensated by changes in hepatic arterial flow thus defini ng the hepatic artery buffer response (HABR). To understand the role of liv er flow in liver atrophy, we measured portal flow and hepatic artery flow a fter different degrees of left portal vein stenosis (LPVS). Surgery was per formed to obtain 0, 43, 48, 59, 68, 72, 78, and 100% LPVS. Systemic and spl anchnic blood flows were measured at 4 h or 7 days after surgery using radi olabeled microspheres. At 4 h, LPVS produced no changes in systemic hemodyn amics. Increasing degrees of LPVS produced a significant decrease in left p ortal flow (P < 0.0001) and a fully compensatory increase in right portal f low (P < 0.0001) without significantly affecting total portal flow Left hep atic artery flaw increased by 210% (P = 0.002), and right hepatic artery fl ow decreased by 61% (P = 0.05) after full LPVS. There was a significant inv erse correlation between portal and arterial flow changes induced by differ ent degrees of LPVS in the left (r(2) = 0.61) and right (r(2) = 0.41) lobes . Despite this HABR, we observed a reduction in left, liver flow (-45%; P = 0.01) and an increase in light liver how (+230%; P = 0.01) with 100% LPVS. At 7 days, a significant decrease in the weight of left liver lobes (-75%; P < 0.0001) and a compensatory increase in the weight of the right lobes ( +210%; P < 0.0001) were observed with 100% LPVS. Left and right liver flows were similar to results measured at 4 h, and HABR was still present. Howev er, when expressed per gram of liver, liver flows were identical to results obtained with sham animals. Reduction in lobar portal flow is accompanied by an increase in ipsilateral hepatic artery flow and a compensatory increa se in portal flow to the rest of the Liver. In a given lobe, when compensat ory HABR is overcome, liver weight changes occur so that at the end total l iver flow per gram of Liver tissue is restored. This suggests that in norma l conditions liver flow is a major regulator of liver volume.