Species differences in the sensitivity of small intestine to the spasmogenic effect of K-free solution.

Abstract

Effect of removal of the external Potassium ion (K removal) was examined on the mechanical response of the ileum isolated from thirteen animal species; monkey, dog, cat, rabbit, guinea pig, rat, mouse, volt, deer, cock, pigeon, frog and toad. In isotonic recording, K removal induced a sustained contraction in ileum isolated from cat and deer, however, a transient contraction followed by a relaxation in the ileum isolated from other species. Readmission of potassium to the K-free solution produced a quick relaxation in the muscles of pigeon, frog, guinea pig, rat and mouse. Ouabain (1×10-5 M) inhibited the relaxation induced by the readmission of K. There were species differences in contractile activity to K removal; the relative height of ileal contraction induced by K removal was in the order of pigeon, frog, vole, dog, cat, deer, monkey, cock, guinea pig, rat, rabbit, mouse and toad, respectively. Furthermore, the magnitude of the contractile responses to K removal in the ilea isolated from the various kinds of animals correlated with the ED50 of ouabain for a contractile response in the ilea from these animals, as reported by Shimizu et al. (1979). These results probably confirm the concept that K removal and ouabain induce a contraction which is due to the inhibition on an electrogenic Na pump in muscle cells of the ileum.