Sodium bicarbonate treatment prevents gastric emptying delay caused by acute exercise in awake rats

Abstract

Physical exercise, mainly after vigorous activity, may induce gastrointestinal dysmotility whose mechanisms are still unknown. We hypothesized that physical exercise and ensuing lactate-related acidemia alter gastrointestinal motor behavior. In the present study, we evaluated the effects of short-term exercise on gastric emptying rate in awake rats subjected to 15-min swimming sessions against a load equivalent to 5% of their body weight. After 0, 10, or 20 min of exercise testing, the rats were gavage fed with 1.5 ml of a liquid test meal (0.5 mg/ml of phenol red in 5% glucose solution) and euthanized 10 min postprandially to measure fractional gastric dye recovery. In addition to inducing acidemia and increasing blood lactate levels, acute exercise increased (P < 0.05) gastric retention. Such a phenomenon presented a positive correlation (P < 0.001) between blood lactate levels and fractional gastric dye recovery. Gastric retention and other acidbase-related changes were all prevented by NaHCO3 pretreatment. Additionally, exercise enhanced (P < 0.05) the marker's progression through the small intestine. In anesthetized rats, exercise increased (P < 0.05) gastric volume, measured by a balloon catheter in a barostat system. Compared with sedentary control rats, acute exercise also inhibited (P < 0.05) the contractility of gastric fundus strips in vitro. In conclusion, acute exercise delayed the gastric emptying of a liquid test meal by interfering with the acid-base balance.

Acute exercise inhibits gastric emptying of liquids in rats: influence of the NO-cGMP pathway

“…Thus, we opted for acute exercise for 15 min with a 2.5 or 5% body weight overload, which characterizes high-intensity activity, with increased levels of blood lactate. Acute exercise protocols stimulate anaerobic lactic metabolism in skeletal muscle cells, disrupt the acid-base balance, and lower blood pH, thus delaying the GE of liquid test meals in awake rats (6). In the present study, acute exercise for 15 min against an overload equivalent to 5% of body weight increased fractional gastric dye recovery.…”

“…Acute exercise was performed according to a previously described protocol (14) that was adapted by our group (6) (Supplementary Table S1). All of the rats initially underwent an adaptation period that consisted of swimming in a cylindrical tank (50 cm deep, 60 cm in diameter) filled with warm water (30°C±1°C).…”

“…The rats in the 2.5% exercised group were euthanized 10 min postprandially. Fractional gastric dye recovery was assayed according to Reynell and Spray (14), a technique that was further adapted by our laboratory (6). After surgical exeresis, the gut was quickly ligated at the esophagus, duodenum, and terminal ileum, and divided into consecutive segments: stomach, proximal small intestine (∼40%), mid small intestine (∼30%), and distal small intestine (∼30%).…”

“…We recently found that acute high-intensity exercise delayed the gastric emptying (GE) of a liquid test meal in awake male rats, a phenomenon that appears to be related to blood academia (6). A positive correlation was verified between blood lactate and fractional gastric dye recovery in exercised rats.…”

“…The administration of an NH 4 Cl-containing meal in control rats induced metabolic acidosis and increased fractional gastric dye recovery to a similar degree as in the exercised group. Pretreatment with NaHCO 3 corrected with lactacidemia and prevented the acute exercise-induced delay in GE (6). In addition, Chang and collaborators (2006) observed that lactate administration to sedentary and exercised rats delayed the GE of liquid per se (7).…”