Effect of insulin on potassium transfer in isolated rat liver

The effect of insulin on the net transfer of potassium between the isolated, cyclically perfused, fasted rat liver and the perfusate was studied. In the absence of insulin approximately 7.5% of liver potassium was lost into the serum during 60 min of perfusion. Insulin, at concentrations of 1.2 and 3.0 x 10 –10 m (mol wt 6,000), inhibited this release. Maximal inhibition (93% at 10 min) was elicited with insulin levels of 1.2 x 10 –9 m and greater. A comparison of liver weights at the end of the perfusions revealed that the control livers were significantly smaller than those treated with insulin. No difference in the concentration of liver potassium between these two groups was found. From these data, together with the results of liver water determinations, it was tentatively concluded that, in addition to potassium, water was also released by the liver cell. Although the metabolic significance of these shifts is not clear at present, their inhibition by low concentrations of insulin strongly suggests a physiological role for insulin in the maintenance of liver potassium and water.