The influence of calcium on the rate of diffusion of sugars through surviving intestine

Abstract

IN previous work on this subject [Macleod et al. 1930; Auchinachie et al. 1930], the fluid bathing the surviving segments of intestine was always sugar-free Tyrode's solution. In view of the well-known effects of electrolytes on the physiological activity of living cells, it was decided to determine whether the selective properties of the intestinal epithelial cells would be affected by varying the composition of the outer fluid. The procedure was the same as in previous experiments except that, as it was necessary to prepare the segments in sugar-free but otherwise normal Tyrode (called "normal Tyrode" in text), each segment was thoroughly washed in Tyrode of the composition to be used for the test, so as to ensure that all traces of fluid, except that whose influence was to be studied, would be removed from the intestine. Rabbit's small intestine was used, and its generally greater permeability in an aboral direction was ruled out by suitable selection of segments for control experiments. The volume of outer fluid was 50 cc., and 4 cc. 0-75 M sugar solution were generally placed in the lumen. RESULTS. When the rates of diffusion of 0-75 M glucose through the walls of segments bathed in normal and in Ca-free Tyrode respectively were compared, the rate was found to be greater in the former case, as the following figures from a typical experiment show: Sol. 45 90 135 mins. Ca-free Tyrode 29 103 185} mg. glucose per Normal Tyrode 49 137 2755 100 cc. fluid.

The influence of electrolytes on the function of the intestinal mucosa

“…

WE have shown that the selective action exerted by the epithelium of surviving intestine on sugar solutions placed in the lumen depends on the presence of Ca ions in the bathing fluid, so that when segments were immersed in Ca-free Tyrode the sugars passed through the intestinal wall in accordance with physical laws [Magee and Sen, 1931]. The present experiments were undertaken as an extension of this work, the objective being to determine whether the rate of absorption of glucose is related in any way to the level of Ca in the blood of the living animal.

…”

The influence of calcium on intestinal absorption

“…It was therefore of interest to study the influence of calcium on the permeability of the intestine. Magee and Sen [1931] showed that the selective permeability of the surviving intestine for glucose requires the presence of calcium ions in the bathing fluid. When the segments were immersed in Ca-free Tyrode, glucose passed out more slowly than xylose; whereas in the presence of calcium, glucose passed out more quickly than xylose.…”