Glycogenolytic and haemodynamic responses to heat-aggregated immunoglobulin G and prostaglandin E2 in the perfused rat liver

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Abstract
Infusion of heat-aggregated immunoglobulin G (HAG) into perfused livers from fed rats caused transient increases in hepatic glycogenolysis and portal-vein pressure, accompanied by a transient increase in hepatic glycogen phosphorylase a content. The hepatic responses to HAG were inhibited by indomethacin (2 .mu.M). In contrast, HAG was without effect on phosphorylase a content and glucose output in isolated hepatocytes. HAG infusion caused a transient decrease in hepatic cyclic AMP. Lowering the extracellular Ca2+ concentration to 6 or 50 .mu.M attenuated markedly the glycogenolytic and hemodynamic responses to HAG; efflux of Ca2+ from the liver was not observed in response to HAG. Co-infusion of the specific platelet-activating-factor antagonist U-66985 (1-O-octadecyl-2-O-acetyl-sn-glycero-3-phosphoric acid 6''-trimethylammoniumhexyl ester) did not attenuate the glycogenolytic response to HAG. Infusion of prostaglandin E2 caused increases in glucose output, portal-vein pressure and the reduction state of the cytosolic NAD(H) redox couple similar to those seen with HAG. The present study suggests that the glycogenolytic activation after HAG infusion may be an indirect consequence of the hemodynamic response of the hepatic vasculature to stimulation of the reticuloendothelial cells of the liver.