LE TRANSIT DIGESTIF CHEZ LE LAPIN. IV. — ESSAIS DE MODÉLISATION DES TRANSFERTS D'UN MARQUEUR RADIOACTIF ENTRE LES DIFFÉRENTS COMPARTIMENTS DIGESTIFS

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Abstract
In 2 previous experiments movements of a radioactive marker (141Ce) within the digestive tract of ad lib fed growing rabbits were described, 4 h following the administration of 141Ce either in solution or deposited on food (pellets). An assay was made with the aim of establishing a model for transfer of the marker between the different digestive segments. A model of the deterministic type was used, the spatial compartments of which corresponded to the following digestive segments: stomach, small intestine, cecum, proximal colon, distal colon. The mathematical calculation led to a description of 2 plausible models involving transfers from place to place in the oral-aboral direction, a recycling reflecting the cecotrophy, a backflow from the proximal colon towards the cecum and eventually, a direct transfer from the samll intestine towards the proximal colon. In terms of mathematics, and when the marker was administered in the form of solution, the transfer from the small intestine to the proximal colon did not improve the model. In terms of physiology and when the marker was given in pellet form this transfer led to a more satisfactory model in agreement with the knowledge of the rabbit''s digestive tract physiology. The application of transfer coefficients to the amounts of radioactivity present in the various compartments allowed a quantitative estimation of digesta movements per time unit. About 95-97% of the digesta from the small intestine moved towards the cecum, 3-5% towards the proximal colon and 16-18% which left the proximal colon, moved back in the direction of the cecum, whereas 82-84% moved towards the distal colon. These examples show the irreplaceable contribution of models in the understanding of the complex movements of digesta at the ileo-ceco-colic intersection.