Abstract
Short-chain fatty acids (SCFAs) are produced by bacterial fermentation in the lumen of colon and some previous studies have suggested that SCFAs enhance the motility of this organ. In the present study, effects of SCFAs (acetate, propionate, and butyrate) on the contractions of circular muscle were examined using strip preparations of rat distal colon. In non-stimulus stage, two different motility patterns were observed; one is contractions with high amplitude and low frequency (0.81 ± 0.03 g, 0.30 ± 0.01 / min) and another is contractions with low amplitude and high frequency (0.12 ± 0.01 g, 12.21 ± 0.15 / min). In the present experiment, effects of SCFAs on the former motility pattern were examined. Propionate dose-dependently increased frequency of the contraction while amplitude was slightly decreased. Mixture of SCFAs at the same ratio of physiological condition (acetate : propionate : butyrate = 15 : 7 : 4) also had the same effects. Acetate or butyrate did not increase the frequency. On the other hand, propionate or butyrate but not acetate dose-dependently induced phasic contraction immediately after the addition and the maximal responses were observed at 1 mM. The propionate(1 mM)-induced phasic contraction was inhibited by preincubation of acetate, atropine, or tetrodotoxin. These results suggest that among SCFAs, propionate most effectively enhances the motility of rat colon and a part of the responses of propionate seems to be mediated via cholinergic nerves. [Jpn J Physiol 54 Suppl:S116 (2004)]
