Stomach Emptying in Rats

Reynell and Spray (1956) described a method for the simultaneous measurements of gastric emptying and intestinal transit of test substances in the rat using phenol red as marker. This simple method can also be ideally used for safety pharmacological assessment of candidate compounds on their side effect potential on gastrointestinal motility. 

Rats weighing 200-300 g are starved for 24 hours, with free access to water before the experiment. They are treated orally or subcutaneously with the test compound 15 min prior to oral administration by gavage of 1.5 ml 0.07% phenol red in 2% car-boxymethylcellulose solution. 15 min later the animal is sacrificed and the stomach is immediately removed. The whole stomach including the stomach content is alkalized with 1 N NaOH and homogenized. The homogenate is filtered, and after precipitation of the protein with 10% trichloroacetic acid, centrifuged for 15 min at 3000 rpm. The concentration of phenol red in the supernatant is measured colorimetrically in a photometer at 546 nm. 

Percentage of stomach emptying (Se) is calculated according to the following formula  

Pa = Concentration of phenol red in the initial solution after addition of equal volumes of 1 N NaOH and trichloroacetic acid ( xg/ml) 

Droppleman et al. (1980) described a simplified method for assessing drug effects on gastric emptying in rats. Three ml of a semi-solid test meal, based on methylcellulose, are given to rats fasted 24 hours prior to the experiment. At a specified time following the test meal, the rats are sacrificed, laparotomized, and the stomachs removed. The full stomachs are weighed on an analytical balance they are opened and rinsed. Excess moisture is removed and the empty 

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