Studies on the transport of small bowel contents. An experimental study in the rat with special reference to the evaluation of non-propulsive intestinal movements.

An earlier study (4) of chyme propagation through the small bowel in conscious rats has revealed that the luminal contents are transported in separate portions, which exchange material only to a limited extent. In the present study this transport pattern was confirmed also after the following changes in the standardized experimental conditions used previously: (a) replacement of the standard radioactive labels (125I-PVP and 131I-PVP) with Na2(51CrO4) and 99Tcm-sulphur colloid, (b) replacement of the test meal with saline and (c) investigation of animals without a preceding starvation period. It was also found that the small bowel propulsion was enhanced when the test substance was infused at a higher rate, and that this change did not affect the exchange of material between the portions. The small mixing was further confirmed in experiments in which shifts of label were made repeatedly at constant intervals throughout the infusion period. Distinct regions in which one of the labels predominated could be demonstrated along the entire small bowel when the time interval was diminished to 30 but not to 20 min.