Dose-Dependent Effect of Angiotensin II on Uterine Smooth Muscle Motility

The analysis of the renin-angiotensin system reveals many facets of physiological, pathophysiological and pharmacological interactions. In order to evaluate de effect of angiotensin II on uterine smooth muscle motility, we performed an experimental study investigating its effect in a dose-dependent manner. Material and Methods: Swiss mouse (n=10) uterus was used for the experiment. The uterus was dissected and sectioned into 3-4 mm rings, which were placed in organ baths with 5 ml Krebs-Henseleit serum at 370C, constantly oxygenated (95% O2, 5% CO2). Electric field stimulation was used to determine contractions. Force transducers (isometric) coupled to a computerized acquisition system were used in order to record the contractions. Results: Calculating the standard baseline oscillations and the oscillations corresponding to the EFC stimulated path, a statistically significant t-test was obtained at p?0.002. The muscle reactivity was tested with angiotensin II 10-5 M, after detecting optimum dose-dependent response. The administration of angiotensin before electrical stimulation significantly increased the responsiveness of the uterine muscle to the electrical stimulation (p<0.001). Conclusion: Ang-II significantly increased muscle contractility stimulated by electric field. The phenomenon may be explained by the increase the available calcium in smooth muscle cells by stimulating angiotensin receptors, and amplify the effect of electrical stimulation.