Abstract: Objective To investigate the effect of low-intensity ultrasound on the contents of endothelin (ET-1) and nitrogen
monoxidum (NO) in uterine tissues of SD rats after abortion. Methods Thirty female pregnant rats were randomly divided
into treatment group and control group and received mifepristone and misoprostol to induce abortion. The rats in the
treatment group were treated by low-intensity ultrasound for 30 min/day for 5 consecutive days, and those in the control
group received sham treatment. The uterine tissue was then taken and homogenized for measurement of ET-1 and NO
contents using enzyme-linked immunosorbent assay and chemical testing. Results ET-1 content in the uterine tissues was
significantly higher in the treatment group than in the control group (P<0.05), but NO content showed no significant difference
between the two groups (P>0.05). Conclusion Low-intensity ultrasound can promote the contraction of uterine smooth
muscles by increasing the level of ET-1 to modulate the homeostasis of ET-1 and NO.