Buffer-Dependent Actions of Insulin and Halothane on Glucose Metabolism in Isolated Rat Atria 1

Abstract

Summary

Rat atria incubated in 25 mM phosphate buffered medium converted glucose to CO₂ at a rate less than half that seen in 25 mM Tris. The stimulatory action of 100 mU/ml insulin and the inhibitory action of 1 mM halothane on CO₂ production from glucose seen in Tris medium did not occur in phosphate buffered medium. A higher concentration of halothane (8 mM) was required to inhibit CO₂ production from glucose in phosphate buffer. In contrast, the rate of incorporation of glucose into glycogen was similar in phosphate and Tris buffered medium. This glucose incorporation is stimulated by insulin and inhibited by halothane in both buffer systems. We conclude that with phosphate as the only buffer glycolysis is inhibited at some site subsequent to the production of G-6-P from glucose, probably at the phosphofructokinase step, and that this inhibition interferes with the actions of insulin and halothane on glucose catabolism.