<Original article>Sympathetic Control of Portal Circulation under Partial Hepatectomy in Rats

The effect of a hepatectomy on the sympathetic control of portal circulation was examined in anesthetized rats. Sympathetic activation was obtained by cerebral ischemia. Cerebral ischemia with carotid arterial occlusion (30s) produced a reduction in the portal venous flow (PVF) in the intact liver rats. When the rats received a partial hepatectomy (40, 66 and 90%), there was a proportional relationship between PVF and liver volume, and a significant decrease in PVF due to cerebral ischemia was obtained when 40% of the liver was resected. Cerebral ischemia failed to change PVF under 66% and 90% hepatectomies. Under hepatectomy, nanomolar quantities of adrenaline injected into the portal vein reproduced a decrease in PVF that was seen after cerebral ischemia. A blood flow reduction due to cerebral ischemia was observed in the superior mesenteric vein when 40% and 66% hepatectomies were conducted. Hepatic arterial and splenic venous blood flow were unaffected by cerebral ischemia with or without hepatectomy. Liver functional parameters in the blood were unchanged before and after cerebral ischemia under hepatic resection. These results suggest that hepatectomy modifies the sympathetic regulation of portal circulation through adrenergic vasoconstriction, and that the neural circulatory system maintains its primary functional efficacy when less than 40% of the liver is resected.