Effect of heat exposure on in vitro intestinal transport and utilization of glucose in the rat.

Intestinal transport and utilization of glucose were studied in vitro in chronically heat-exposed (Ta = 34 degrees C) rats. Despite mucosal tissue per centimetre being significantly reduced following 7 and 14 days of exposure, no differences from control values were noted in full serosal to mucosal (S/M) fluid glucose concentrations ratios obtained from everted sac preparations. Measurements on 40-cm jejunal segments perfused in vitro at days 13-15 showed a reduction in the rate of glucose absortpion per centimetre of intestine, while glucose absorption per gram of tissue was unaltered in heat-exposed rats. At the same time, glucose secretion at the serosal surface was unchanged as calculated per centimetre of intestine and increased when calculated per gram of dry tissue. The utilization of glucose by the intestine was found to be significantly reduced whether expressed for intestinal length or for intestinal weight. In addition, the glucose concentration of the tissue water was elevated in intestinal segments of heat-exposed rats after 60 min of perfusion. The decrease in glucose uptake per centimetre of intestine was attributed to the decrease in mucosal tissue. Elevated tissue glucose concentration and enhanced translocation of glucose to the serosal surface were attributed, at least in part, to the decreased rate of glucose metabolism observed in intestines of heat-exposed rats.