Abstract:

[Objective] This study was conducted to explore the effects and possible mechanisms of citric acid and acetic acid on the contraction of isolated mouse intestinal smooth muscle, and to provide references for the development of organic acid products that helps regulate gastrointestinal motility disorders in humans or animals. [Method] A biological signal processing system was used to monitor the effects of two-fold increasing concentrations of citric acid （0.02-0.64 mmol/L） or acetic acid （0.13-2.00 mmol/L） as well as their corresponding bolus effective concentrations on the contractile amplitude, ension, and peak of the isolated intestinal segment in mice. [Result] Both citric acid and acetic acid dose-dependently reduced the contractile amplitude and tension of the intestinal smooth muscle （P<0.01）, with the effective inhibitory concentrations of 0.32 mmol/L and 1.00 mmol/L, respectively. Both acids with effective inhibitory concentrations did not affect the contractile peak of the intestinal tissue caused by 25 mmol/L KCl （P>0.05）, while the citric acid treatment significantly （P<0.05） alleviated the decrease in intestinal contractile amplitude induced by bethanechol chloride, an M-receptor agonist. [Conclusion] Both citric acid and acetic acid can inhibit the contraction of isolated intestinal smooth muscle in mice, and may not affect the depolarization process of smooth muscle cell membrane. However, citric acid may have spasmolytic effect on gastrointestinal smooth muscle via partially affecting the role of M-receptor.

Key words: citric acid, acetic acid, mouse, intestine, smooth muscle, M-receptor