Comparison of two orogastric feeding markers for measuring gastrointestinal motor functions in rats

Rat gastrointestinal (GI) transit parameters measured with charcoal and radiochromium were compared. Animals were fed with a calorie-free liquid test meal which contained 10% charcoal and radiochromium (0.5 microCi ml-1) via a transiently placed orogastric catheter. The rats were sacrificed at 1, 5, 15, 30, 60 and 120 min, respectively, since feeding. Various motor parameters were measured. Charcoal transit ratio, gastric emptying and geometric center were time dependent. Charcoal transit ratio occasionally showed a positive correlation with gastric emptying in the very late experimental periods. Concerning the correlation of charcoal transit ratio and geometric center, negative and positive correlations were seen in the very early and late periods, respectively. We conclude that the rat charcoal transit ratio has limited value to replace the GI transit parameters determined by feeding radiochromium.