Role of nitric oxide in glucose-, fructose and galactose-induced increases in intestinal glucose uptake

Abstract

Previous studies have shown that the infusion of glucose, fructose and galactose resulted in significant increases in intestinal glucose uptake (IGU) and the role of nitric oxide in these responses was not known. The present study was designed to investigate the role of nitric oxide in the observed increases in IGU. Experiments were carried out on thirty-five (35) fasted male anaesthetized Nigerian local dogs divided into seven groups (5 dogs per group). Group I dogs served as control and received normal saline, groups II-IV dogs were infused with glucose (1.1 mg/kg/min), fructose (1.1 mg/kg/min) or galactose (1.1mg/kg/min) while groups V-VII were pretreated with L-Nitro-Arginine-Methyl-Esther (L-NAME) (35 mg/kg) after which they were infused with glucose (1.1 mg/kg/min), fructose (1.1 mg/kg/min) or galactose (1.1mg/kg/min). Through a midline laparatomy, the upper jejunum was cannulated for blood flow measurement and blood samples were obtained for measurement of glucose content of the arterial blood and venous blood from the upper jejunal segment. Glucose uptake was calculated as the product of jejunal blood flow and the difference between arterial and venous glucose levels (A-V glucose). Blood pressure was recorded continuously. The results showed that pretreatment of the animal with L-NAME, caused significant reductions in jejunal blood flow with complete abolition of glucose-, fructose- and galactose-induced increases in IGU. The results suggest that only glucose-induced IGU was nitric oxide-dependent through the induced hyperemia while the increases in IGU caused by fructose and galactose were not mediated by nitric oxide.

Keywords: L-Nitro-Arginine-Methyl-Ester, Hexoses, Haemodynamics, Glucose uptake