Studies Done in Single Rats, Simultaneously Comparing Disappearance Rates of Compounds from Different Regions of the Small Intestine

Abstract

Presented here are a) a simple procedure for measuring regional permeability differences of compounds in the small intestine of a single rat, and b) preliminary study to test the procedure utilizing seven different benzoic acids, e.g. benzoic acid, o-hydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, 3,5-dinitrobenzoic acid, and 2,5-dihydroxybenzoic acid. Rates of disappearance (absorption) of these compounds were measured simultaneously in upper and lower segments of the small intestine using this variation of the in situ rat gut absorption study technique. Under the experimental conditions used, disappearance rate of a given compound was no different from upper or lower segment for any of the compounds except for p-hydroxybenzoic acid. The latter disappeared about three times faster from the upper than lower segment. Not only is this experimental procedure of utility in differentiating regional permeability within the intestine. It offers the option of testing the effect of an additive or other environmental change on compound permeability, while the other segment serves as a control.