Effect of caloric content and composition of a liquid meal on gastric emptying in the rat

We examined the effect of caloric content and substrate composition on gastric emptying in conscious Sprague-Dawley rats using gastric radioscintigraphy. Three-milliliter volumes of normal saline, glucose, casein hydrolysate, or intralipid containing 0, 1, 2, 3, or 6 kcal labeled with ^99mTc-diethylenetriaminepentaacetic acid were given intragastrically. Gamma-camera imaging and computer analysis allowed construction of gastric emptying curves constructed over many time points for each emptying study. There was no difference in the half-emptying times (t( 1/2 )) between different substrates with equal calories, and increasing calories significantly prolonged gastric emptying for all substrates. Emptying occurred in a linear fashion with meals containing calories. With 3-ml meals containing 2, 3, or 6 kcal, the rate of delivery of calories to the duodenum is constant regardless of substrate or change in caloric content. We conclude that the rate of caloric delivery to the small intestine with gastric infusion of 1-6 kcal is relatively constant despite differences in total caloric load, substrate composition, and osmolarity.