An Experimental Study: Low Intensity Ultrasound On Inducing Contraction In Vitro Uterine Smooth Muscle

Objective:To study the influence and dose-effect relationship of low intensity ultrasound on the contraction of uterine smooth muscle in rats and to find optimal exposure parameters; To find the experimental evidence of low intensity ultrasound in postpartum hemorrhage prevention and treatment.Methods: 1. The isolated uteri were irradiated with ultrasound (frequency 0.8MHz , focal distance 117mm) of different intensity(1W/cm2,2W/cm2,3W/cm2)and exposure time(5min,10min,15min,20min,25min,30min)by the way of orthogonal design. The contraction frequency, amplitude, tension and activity were noted with BL-410 biological experimental system and the changes of the temperature were measured, after that we observed the histopathologic alterations by light microscope and ultramicrostructure by transmission electron microscope to explore the optimal suitable parameters. 2. The isolated uteri of forty SD rats were randomly divided into 4 groups: group A (normal control group), group B (ultrasound group), group C (oxytocin group) and group D (ultrasound + oxytocin group), their contraction information was recorded to explore the disparity among them.Results:1. It could be seen that the contraction frequency, amplitude, tension and contraction activity were significantly increased under ultrasonic irradiation(p<0.05); The contraction frequency, amplitude, tension and contraction activity peaked at 2W/cm2 ultrasonic irradiation for 10 minutes.2. The histological structure and ultramicrostructure of the uterine smooth muscle did not have an abnormal change under the ultrasound of intensity of 2W/cm2 for 10 minutes and the temperature change of uterine smooth muscle was 3℃.3.The contraction frequency,tension and contraction activity of group B, group C and group D were superior to group A(P<0.05); The contraction frequency,tension and contraction activity of group C were superior to B group(P<0.05); The contraction frequency,amplitude and contraction activity of group D were superior to group B(P<0.05); The contraction amplitude and contraction activity of group D were superior to group C(P<0.05).Conclusion:1. Low intensity ultrasound can induce uterine smooth muscle contraction in rats.2. With constant frequency of 0.8MHz, the optimal parameter is 2W/cm2 ultrasonic irradiation for 10 minutes. 3. Low intensity ultrasound can intensify the function of oxytocin and the contraction frequency, amplitude, tension and contraction activity were significantly increased under its irradiation.