Regulation of oxygen consumption in perfused rat liver: decrease by alpha-sympathetic nerve stimulation and increase by the alpha-agonist phenylephrine.

In livers perfused with Krebs-Henseleit bicarbonate buffer containing bovine red cells, 5 mM glucose and 2 mM lactate, electrical stimulation round the hepatic artery and the portal vein caused via alpha-receptors a decrease in oxygen consumption and portal flow, an increase in glucose output and a switch from lactate uptake to output. In livers perfused with erythrocyte- and substrate-free buffer both in a volume- or pressure-constant system stimulation of the liver nerves resulted in similar changes. Infusion of the alpha-agonist phenylephrine mimicked the metabolic and hemodynamic nerve effects, but led to an increase in oxygen uptake. The converse effects of alpha-sympathetic nerve stimulation and alpha-agonist infusion on oxygen consumption indicate either a different mode of action or a complex mechanism with opposing metabolic and hemodynamic components.