Glucose Penetration Into Liver

Abstract

To further define the action of insulin on liver metabolism, studies were undertaken to determine whether the cell wall could be the site of action as has been proposed for muscle. Control rats and those injected with varying amounts of glucose were found to have a higher glucose concentration in liver water compared to plasma water with low plasma glucose levels and vice-versa with high plasma glucose levels. Radioactive glucose was freely distributed into total liver water in dogs whether the liver was taking up or producing glucose. Other compounds which entered rat liver cells were fructose, mannose, galactose, sorbitol, mannitol, glycerol and α-methyl glucopyranoside. Maltose, sucrose and raffinose were restricted to extracellular fluid. Alloxan diabetic rats likewise showed free equilibration of radioactive glucose between plasma and liver water. The free permeability of liver to glucose and other small carbohydrates suggests that insulin in liver alters intracellular enzyme functions and not permeability of the cell wall as in muscle.