Oxidation-Reduction Potentials of the Contents of the Gastrointestinal Tract

Abstract

Little work has been reported on oxidation-reduction potentials in the gastro-intestinal tracts of men or animals, in spite of the fact that the intestines are known to be the site of powerful reduction processes associated particularly with bacterial actions occurring therein. These oxidation-reduction potentials may be expected to be of influence on some of the numerous chemical reactions taking place in the gastrointestinal tract. Besides being a reflection of the intensity and character of bacterial growth, the potentials may influence the nature and extent of such flora. Bergeim (1924) reported observations on the reduction of hydrated ferric oxide in the gastrointestinal tract under various conditions of diet, giving a semiquantitative measurement of reduction intensities. Actual measurements of oxidation-reduction potentials were not however carried out. The present paper gives the results of some observations on the oxidation-reduction potentials in different parts of the gastrointestinal tract of animals as influenced by diet and by certain sulfonamides. It is, of course, realized that the potential measurements do not tell us anything as to the amount or exact nature of the reducing substances present and are in this sense preliminary in nature. They do however serve to define the usual limits of reduction intensity in the gastrointestinal contents and to indicate whether or not very small amounts at least of a given substance are likely to be reduced in a certain section of the tract. EXPERIMENTAL Albino rats, about 150 g in weight, were fed various diets for periods of from a few days to several weeks. The animals were then killed and material collected from the stomach, the upper half of the small intestine, the lower half of the small intestine, from the cecum, and from the colon. Oxidation-reduction potentials were determined on these materials by using a bright platinum electrode (Beck-mann no. 1281 with 5-mm-square platinum foil checked at intervals against a standard quinhydrone solution) and a potentiometer (Leeds and Northrup 4661-Al). Determinations were begun immediately after death, starting with the contents of the stomacb and following with those of the small and then of the large intestine. Material was left in the organ until just before the estimation was to be started. The stomach or intestine was then cut open and the contents carefully squeezed out. Determinations were made in open dishes exposed to air and at room temperature. The room temperature varied from 25 to 28 C. No temperature correction was made since such correction would have been with-453