Isolation buffer calcium concentration and subsequent acute effects of insulin on metabolism of perfused rat liver.

During the surgical isolation for subsequent perfusion in situ with blood containing 1.3 mM Ca, livers from fed male rats were perfused with buffer containing 1.3 or 3.6 mM Ca. Total liver Ca was unaffected by buffer concentration and did not differ from non-perfused controls. In all groups a negative relationship was found between serum Ca and K+ concentrations and serum K+ was depressed by insulin and high buffer Ca while serum Ca was raised by the latter. Blood glucose was raised by isolation at high buffer Ca but was lowered by insulin with an increase in liver glycogen in both groups. Ketogenesis was unaffected by buffer Ca and was inhibited by insulin. The hormone raised serum triacylglycerol secretion and liver triacylglycerols in both groups, but the latter increase was abolished at the higher buffer Ca concentration. This effect on liver triacylglycerols may be related to the rise in microsomal Ca-ATPase activity found in these livers. We conclude that use of high concentrations of Ca in the isolation buffer, which may maintain hormone sensitivity in isolated hepatocytes, is not advantageous to the subsequent perfusion of the isolated liver with undiluted blood.