Some in vitro studies of changes in short-circuit current of the rat small intestine induced by sugars

Abstract

The concepts of intestinal sugar transport are almost continuously changing and the detailed mechanisms are not yet fully understood. An attempt has been made to obtain some further information from the study of changes in the short-circuit current measured by a modified technique introduced for the everted intestinal segments of the rat.

Different concentrations of a variety of sugars, some actively transportable, some non-actively transportable and some disaccharides have been tested at 37°C. Glucose and galactose were tested at different temperatures.

The sugar derivatives, ethylidene glucose and benzylidene glucose were found to inhibit competitively the active transport mechanism. Similar inhibition was observed with mannose and lactose. These four compounds form a group of non-transportable sugar inhibitors.

Kinetic analysis was made from the above studies and the Kis and the DeltaI maxs were determined for most of the tested sugars including the non-transportable ones.

In the presence of a metabolized sugar (glucose) the intestinal segment maintained its viability over a period of about three hours without a marked effect of the duration. Addition of citrate as a source of metabolic energy improved the level of short-circuit current in the presence and absence of galactose. Anoxic conditions were more effective in depressing the short-circuit current levels in the presence of galactose than in the presence of glucose.

The short-circuit current steady state, once it was established, remained stable throughout the experiment and in the presence of 3-0-methylglucose was approximately equal to the net Na+ flux from mucosa to serosa.

Approximately a1 : 1 stoichiometric relationship between Na+ (ionic-current) and 3-0-methylglucose was observed within a certain range of sugar concentration.