Effect Of Low-intensity Ultrasound To Uterine Involution After Medical Abortion In The Early Pregnat Rats And A Preliminary Study Of Its Mechanism

Objectives1. To observe the effect of uterine involution in aborted rats radiated bylow-intensity ultrasound. And analysis the effect of Low-intensityUltrasound to uterine involution.2. To investigate the possible mechanisms of Low-intensity Ultrasoundto promote uterine involution in rats which were aborted in early pregnant.Methods1. We randomly selected55numbers of female ordinary-level SD rats,all of them were less than3months of age. And5numbers of maleordinary-level SD rats. Caged with proportion of male and female2:1atnight (20:00). Observe vaginal plug after12hours (at8:00in the next day).Then observe sperm in the vaginal smear under the microscope. The day ofobserved vaginal plug or sperm is the first day of pregnancy. Otherwise, after7days of male and female rats separated, repeating the same method until itwas pregnant again. The first seven days of rat pregnancy, administered 16.6mg/kg of mifepristone at8:00and0.1mg/kg of misoprostol at18:00.Established30numbers of the model of completely aborted in early pregnantrats.2.30numbers of the model of trimester abortion randomly divided intoultrasound radiation and sham radiation groups each15. From the first day ofabortion, the rats in the ultrasound radiation group were treated byLow-intensity Ultrasound (Sound intensity=2W/cm2, Frequency=0.8MHz)for30min/day for5consecutive days, and those in the sham radiation groupreceived sham treatment (Sound intensity=0W/cm2, frequency=0MHz).3. After Gestational sac discharged, built-in a quantitative tampon intorat’s vaginal with eye tweezers. Taken out the bleeding cotton every2-6hours, detect the amount of bleeding and record the bleeding time.4. The next day after the end of the treatment. Take the size of soybeanof left uterine tissue in rats3pieces. endothelin-1(endothelin-1, ET-1),nitric oxide (nitrogen monoxide, NO) and oxytocin receptor (oxytocinreceptor, OTR) were detected by ELISA, chemical assays andimmunohistochemistry, respectively.Results1. Pregnancy success rate was41.7%(40/96). In three methods, thesensitivity of vaginal plug+sperm examination is the highest (0.9000), andshowed indistinct difference with sperm examination (0.8750). But thesensitivity of vaginal plug examination (0.7000) is the lowest. Specificity of three methods is of less difference.The false negative rate of vaginal plugexamination is up to30.00%. The differences were statistically significantcompared with sperm (12.50%) and vaginal plug+sperm (10.00%)(*P<0.05). The false positive rate of three methods was no significant difference(P>0.05). The success rate of medical abortion is88.24%(30/34).2. Eye view: In sham radiation group, there was no gestational sac fossain uterus. However, the uterus in sham radiation group is greater than it is innormal rats about2mm~3mm. The surface of uterus was hyperemiasignificantly and looks cherry red. In ultrasound radiation group, uterus ofRats returned to normal state. Pathology: In ultrasound radiation group,uterine muscle fibers slender, muscles inside arranged in a ring and theoutside longitudinal. In sham radiation group, uterine muscle fiber were mildhypertrophy and arranged a little disorder. Myometrium is thicker than it isin ultrasound radiation group, and uterine cavity is bigger than that in theultrasound radiation group.3. Comparison of vaginal bleeding and bleeding time, Compared thetwo groups, Vaginal bleeding of ultrasound radiation group was less than itwas in sham radiation group, the difference was statistically significant (*P<0.05); But vaginal bleeding time showed no significant differences betweenthe two groups (P>0.05).4. ET-1content in the uterine tissues was significantly higher in theultrasound radiation group than in the sham radiation group, and with statistical significance (*P <0.05). However, NO content in the uterinetissues was less in the ultrasound radiation group than in the sham radiationgroup, but no statistically significant (P＞0.05).5. Expression of OTR was positive in ultrasound radiation and shamradiation group. But most uterine tissues in ultrasound radiation group werestrong positive expression, and most uterine tissues in sham radiation groupweakly positive expression. In myometrium and endometrium of uterus,strong positive expression rate of OTR was higher in ultrasound radiationgroup than that in sham radiation group. The difference was statisticallysignificant (*P <0.05).Conclusion1. Sperm examination which is simple, easy to master and highsensitivity, is the best method to determine whether female rats werepregnant.16.6mg/kg dose of mifepristone+0.1mg/kg dose of misoprostolwith the high success rate in establishing the model of complete abortion inrats.2. Low-intensity Ultrasound (Sound intensity=2W/cm2, Frequency=0.8MHz) could promote uterine involution when acting on uterus that werecompletly aborted in rat.3. Increasing ET-1levels, adjustment the balance of ET-1and NO inuterine tissue may be an important way for Low-intensity Ultrasound topromote uterine contractions. 4. The mechanisms of Low-intensity Ultrasound promote uterinecontractions was related to increasing expression of oxytocin receptor inmyometrium and endometrium of uterus.