An Experimental Study: Low Intensity Ultrasound Induced Human Postpartum Uterine Smooth Muscle Contraction In Vitro

Objective:To study the influence of low intensity ultrasound on the contraction of human postpartum uterine smooth muscle in vitro and to find the mechanism of the uterine smooth muscle contraction by ultrasound irradiation. To find the experimental evidence of low intensity ultrasound in postpartum hemorrhage prevention and treatment.Methods: 1. The human postpartum uterine smooth muscle were irradiated by low intensity ultrasound (0.8MHz,2W/cm2) for 10 min. The contraction frequency, amplitude, tension and activity were noted with BL-420 biological experimental system and the changes of the temperature were measured, after that the histopathologic alterations were observed by light microscope and transmission electron microscope to explore the optimal suitable parameters. 2. The forty samples 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. 3. Added the chelating agent of ecto-calcium , blocking agent of calcium-store receptor,blocking agent of calcium channels respectively in nutritive medium.Then the human postpartum uterine smooth muscle were irradiated by low intensity ultrasound (0.8MHz,2W/cm2) for 10 min to observe the changes of contraction frequency, amplitude, tension and activity.Results:1. It could be seen that the contraction frequency, amplitude, tension and contraction activity were significantly increased under 2W/cm2 ultrasonic irradiation for 10 minutes(p<0.05).2. The histological structure and ultramicrostructure of the uterine smooth muscle did not have an abnormal change under the ultrasound of 2W/cm2 for 10 minutes and the temperature increased for 3℃.3.The contraction frequency, amplitude, 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,tension 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).4. After added the chelating agent of ecto-calcium( EGTA),the contraction frequency, amplitude, tension and contraction activity were significantly decreased under 2W/cm2 ultrasonic irradiation for 10 minutes(P<0.05).After added the blocking agent of VDCs(Nifedipine) ,the contraction frequency, amplitude, tension and contraction activity were significantly decreased under 2W/cm2 ultrasonic irradiation for 10 minutes(P<0.05). After added other ones,there was no obvious change in the contraction frequency,amplitude,tension and contraction activity(P>0.05).Conclusion:1. Low intensity ultrasound can induce human postpartum uterine smooth muscle contraction in vitro.2. Low intensity ultrasound can intensify the function of oxytocin and the contraction frequency, tension and contraction activity were significantly increased under its irradiation.3. The mechanism of enhancing the uterine smooth muscle contraction by low intensity ultrasound irradiation was mainly relevant to activating the VDCs which consequently promoting the inflow of ecto-calcium.