SIMULTANEOUS DETERMINATION OF GASTRIC-EMPTYING AND INTESTINAL-ABSORPTION DURING CYCLE EXERCISE IN HUMANS

Because fluid absorption values derived from intestinal perfusion may not represent intestinal absorption of the same solution following its oral ingestion, the present study measured intestinal absorption foll owing oral ingestion of a beverage. To do so required the simultaneous determination of gastric emptying. Seven males positioned a nasogastr ic tube in the gastric antrum and a multilumen tube in the duodenum un der fluoroscopic guidance. Gastric emptying (GE) and intestinal water flux (WF) were measured during 85 min of cycle exercise at 60.6 +/- 3. 7% VO(2)max (x +/- SE) in a 22 degrees C environment. Subjects ingeste d a total of 23 ml . kg(-1) body weight (2005 +/- 187 ml) of a 6% isot onic carbohydrate-electrolyte solution by drinking 396 +/- 34 ml 5 min prior to exercise followed by 198 +/- 17 ml every 10 min during exerc ise. Mean stomach volume (312 +/- 80 ml) and GE (19.7 +/- 2.0 ml . min (-1)) did not change significantly after the initial 35 min equilibrat ion period. Mean WF during oral ingestion of the solution (19.5 +/- 2. 6 ml . cm(-1). h(1)) did not differ significantly from mean WF (16.4 /- 1.9 ml . cm(-1). h(-1)) during perfusion of the same solution direc tly into the duodenum at a rate equal to each subject's GE rate. Total solute flux (mmol . cm(-1). h(-1)) was not different between drinking (4.1 +/- 1.3) and infusion (3.8 +/- 1.0) trials, nor were the changes in plasma volume. Urine production immediately following the exercise bout was unchanged between drinking (89.1 +/- 27.5 ml) and perfusion (88.5 +/- 24.2) experiments. These data indicate that: 1) relatively c onstant stomach volumes can be maintained over a prolonged period of t ime and can produce relatively constant GE rates, and 2) intestinal ab sorption of an isotonic carbohydrate-electrolyte beverage can be accur ately determined by a modified segmental perfusion technique employing ingestion rather than intestinal perfusion.