Cholera toxin stimulates absorption of d-glucose from the adult rabbit small intestine in vivo

Abstract

Objective: Determine the effects of purified cholera toxin (CT) on intestinal absorption of glucose. Glucose is known to stimulate intestinal sodium absorption which provides the basis for the glucose-containing oral rehydration solution for the treatment of diarrhoea. Although this physiologic mechanism is. well-preserved daring severe cholera, the effects of purified cholera toxin on intestinal absorption of glucose itself has not been evaluated. Methods: In this study, carried out in the facilities of the ICDDR,B's Dhaka-based Animal Resources Branch, the effects of CT on the absorption of glucose from the small intestine of anaesthetized rabbits were evaluated. In the duodenum, 1-2 microgram of purified CT (Sigma) was added after laparotomy and was incubated for 18 hours. After the incubation period, the segment was flushed with phosphate-buffered solution; 10 ml of the soultion containing 0.25 g of D-gtucose was injected into the duodenum, and peripheral blood glucose was monitored every 10-15 minutes using specific method for detection of D-glucose. Results: The results indicate that there was a progressive increase in the concentrations of glucose in the CT-treated rabbits over a period of 120 minutes, and the concentrations were significantly higher (p<0.001) than that in the control rabbits treated with glucose-free saline (blood glucose: 10*3 ± 3.5, 260 ± 13.9, 274 ± 18.0, 317 ± 18.8, 415 ± 38.6, 375 ± 22.5, 350 ± 18.4, 327 ± 7.1 mmol/1 (mean ± SD) for CT-treated rabbits vs. 109 ± 5.5, 156 ± 4.9, 187 ± 4.7, 224 ± 4.6, 260 ± 6.9, 257 ± 5.7, 243 ± 4.8, 228 ± 5.7 mmol/1 for the control rabbits across all periods). A higher dose of CT (1 pg vs. 2 ug) significantly produced better stimulation (p<0.01) of intestinal glucose absorption. The CT-specific rises in glucose concentrations ranged between 41.5% and 66.6% during the 120 minutes. Conclusions: These preliminary results indicate that CT induces dose-dependent glucose absorption from the small intestine of rabbits. To explain these effects of CT, it is speculated that this action may be mediated through the stimulation of glucose transport mechanism in apical membrane, involving the carrier proteins. Further studies will be needed to explore these hypotheses