Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA218

Poster Communications

Intestinal modulate of glucose homeostasis in mongrel dogs

A. A. Alada1, S. T. Shittu1

1. Physiology, University of Ibadan, Ibadan, Oyo, Nigeria.

Previous studies (Alada and Oyebola, 1996; Grayson and Oyebola, 1983) have shown that the intestine increased its glucose uptake during hyperglycemia and released glucose into circulation during insulin-induced hypoglycemia. This study was designed to investigate the metabolic fate of the increased glucose taken up by the intestine in response to hyperglycemia and the source of glucose released into circulation during hypoglycemia. Experiments were carried out on fasted, male, adult mongrel dogs anaesthethized with intravenous injection of sodium pentobarbitone (30.0mg/kg) and divided into three groups with 5 dogs per group. Groups I-III received i.v infusion of normal saline (0.1 ml/kg/min), glucose (20mg/kg/min) and insulin (8 iu/kg/min) respectively. Through a midline laparatomy, the upper jejunum was secured and cannulated for blood flow measurement. Blood samples were obtained for measurement of glucose and lactate from the upper jejunal segment.The plasma glucose and lactate were enzymatically determined. Intestinal glucose/lactate uptake was calculated as the product of jejunal blood flow and arterio-venous glucose /lactate difference. Values are means ± SEM, compared by ANOVA and Student t-test. Jejunal tissue glycogen was determined by Anthrone method while activities of glycogen synthase, phosphorylase and glucose-6-phosphatase were measured spectrophotometerically. Glucose increased the intestinal glucose uptake from 14.5 ± 6.4 mg/min to 142.2 ± 17.9 mg/min while insulin caused a negatve uptake of 71.8 ± 10.6 mg/min. Intestinal lactate uptake increased from 36.4 ± 5.8 mg/min to -77.8 ±12.3 mg/min and 60.8 ± 9.2 for glucose and insulin respectively. Jejunal glycogen content increased from 138.7 ± 4.6 mg/100g to 165.5 ± 10.6 mg/100g for glucose and reduced to 97.4 ± 4.3 mg/100g for insulin. Intestinal phosphorylase activity increased in response to insulin and decreased significantly in response to gucose. While glucose had no effect on intestinal glycogen synthase activity, insulin significantly reduced it. Also, insulin increased glucose-6-phosphase activity while glucose reduced it. The results suggest that the small intestine modulates blood glucose levels through oxidation, glycogen formation and conversion of lactate to glucose.

Where applicable, experiments conform with Society ethical requirements