Effect of the beta-adrenergic blockade on intestinal lactate production and glycogen concentration in dogs infused with hexoses

Abstract

To investigate effect of beta adrenergic blockade on intestinal lactate production and glycogen concentration in dogs infused with hexoses. Experiments were carried out on 35 fasted male anaesthetized dogs weighing between 9 and 16kg. The animals were divided into 7 (5 dogs per group) groups. Group I dogs served as control and infused with normal saline, groups II-IV were intravenously infused with glucose (1.1mg/kg/min), fructose (1.1mg/kg/min) and galactose (1.1mg/kg/min) respectively while groups V-VII animals were pretreated with propranolol (0.5mg/kg) and were infused with glucose, fructose or galactose respectively. A vein draining the proximal segment of the jejunum was cannulated along with right and left femoral arteries and veins. Glucose uptake was calculated as the product of jejunal blood flow and the difference between arterial and venous glucose levels (A-V glucose), part of the jejunum tissue was homogenized for estimation of glycogen concentration, and plasma lactate was assayed using lactate colorimetric kit. The result showed significant increase in venous lactate production in response to glucose (78.30±4.57mg/dL), fructose (60.72±1.82mg/dL) and galactose (71.70±1.30mg/dL) when compared with the control group (51.75±1.32mg/dL) at (p<0.05) with no significant difference in animals pretreated with propranolol. There was no significant difference in glycogen concentration (p>0.05) in animals infused with hexoses only compared with propanolol pretreated group. Results suggests that one of the possible fates of the enormous amount of glucose taken up by the intestine is conversion to lactate and not glycogen and β-adrenergic receptor does not affect it.