Identical orocecal transit time and serum motilin in hyperthermia and normothermia

Fever, exercise, and exposure to a hot environment can all cause symptoms of gastrointestinal dysfunction as they elevate body temperature. Nonetheless, the link between hyperthermia per se and these symptoms is unknown. To test the functional significance of increased body temperature, we investigated the influence of substantial passive hyperthermia on orocecal transit in 12 young, healthy men. Transit time was determined by a consistent rise in H2 concentration in a rebreathing apparatus after oral ingestion of 0.7 g lactulose/kg body weight. Lactulose was given in combination with a 350-ml liquid meal (360 kcal). After raising core temperature in warm water to 38.3 degrees C, orocecal transit time was identical to control (90 +/- 13 min at 38.3 degrees C, 92 +/- 13 min at 37.1 degrees C). While hyperthermia did elevate heart rate and minute ventilation, serum motilin, gastrin, and cortisol were similar in the two conditions. The failure of a passive core temperature rise to alter mouth-to-cecum transit suggests that this aspect of alimentary function is independent of body temperature.