Regulatory effects of insulin and liver on brain glucose metabolism.

Abstract

Glucose uptake and metabolism in brain have been studied in 3 groups of eviscerated rats: 1) hyperglycemic rats with insulin deficiency (infused with glucose, 15 mg/100 g/ hr); 2) normoglycemic rats with sufficient insulin (infused with glucose, 50 mg/100 g/hr, and insulin); and 3) hypoglycemic rats with insulin excess (infused with glucose, 25 mg/100 g/ hr, and insulin). In the insulin-deficient rats, glucose accumulated in brains to concentrations 6 times those found previously in normal rats, and the brain/blood ratio of glucose concentrations was increased 3-fold. In these rats the glucose uptake in brain at 15 min after injection of glucose-U-14C was 6.08 μmoles/g (expressed as blood glucose equivalent) and was similar to that in normal rats, but the glucose metabolites in brain represented only 2.88 μmoles/g or half that in normal rats. Thus, glucose accumulated in brains of the hyperglycemic eviscerated rats because of decreased utilization. In the normoglycemic rats the glucose concentration in br...