Rat small intestinal transit is independent of glucose consumption in the strenuous exercise

The present study was to determine the effect of strenuous exercise on glucose utilization, lactate accumulation and small intestinal transit (SIT). In strenuous exercises, rats would be put on the runway of a moving treadmill for a one-hour compulsive running. Rats first performed running treadmill for 45 min. After orogastric feeding of radiochromium marker, they resumed running for additional 15 min until sacrifice to measure SIT. Saline and various doses of glucose and lactate were infused through previously placed jugular vein during the whole procedure. Blood was finally obtained to measure plasma glucose and lactate levels. Saline infusion had no effect on running rat SIT during strenuous exercise, but plasma glucose level was significantly lowered (P < 0.01). Infusion of various doses of glucose did not alter SIT during strenuous exercise; however, the initially lowered plasma glucose was restored even to a hyperglycemic state. Meanwhile, strenuous running markedly increased plasma lactate level, irrespectively of saline or glucose infusion (P < 0.01). Lactate infusion did not change rat SIT obtained on the quiet runways. In conclusion, rat SIT remained unchanged in the strenuous exercise although obvious hypoglycemia and higher plasma lactate level did exist. Glucose utilization and lactate accumulation after the strenuous exercise may not directly mediate small intestinal motility.