Carbohydrate metabolism and its response to catecholamines as modified in alkalotic rat

Metabolic activities and their responses to catecholamines were studied in fasted rats exposed to simulated altitudes. Analysis of hepatic levels of gluconeogenic intermediates revealed the inhibition of gluconeogenesis between glyceric acid 3-P and fructose 6-P associated with a rise of the ratios of redox pairs such as lactate to pyruvate in livers of alkalotic rats. Inhibition of gluconeogenesis was indicated also by the suppressed incorporation of glutamate 14C into blood glucose. Since no activation was detected on glycolytic pathway of skeletal muscles, marked hyperlactacidemia during alkalosis appeared to result from the suppression of hepatic gluconeogenesis. Most of metabolic actions of epinephrine and isoproterenal known to be mediated via the beta receptor were significantly reduced but not completely abolished during alkalosis. Exceptionally, hyperinsulinemia induced by isoproterenol was completely reversed and replaced by hypoinsulinemia during alkalosis. Despite hypoinsulinemia, hyperglycemia induced by glucose load decreased more rapidly in alkalotic than in normal rats. In view of the fact that the adrenergic alpha receptor is involved in theinhibition of insulin secretion, the observed irregular modifications of catecholamine actions could be explained on the basis of a postulate that the adrenergic alpha-receptor functions are potentiated in alkalosis.