| In assisted reproductive technologies, high-power transvaginal ultrasonography is increasingly used to observe follicle growth or multifetal pregnancy reduction in the early stages of genesis. Its potential bioeffects for conceptus should be paid more attention. An understanding of mechanism by which bioeffect of ultrasound is produced is indispensable for prudent use. However, little is known about bioeffects of transvaginal ultrasound on early conceptus and the mechanism by which biological effects are produced. Our objective is to investigate the effect of exposure of human chorionic villi to transvaginal ultrasound in the first trimester of pregnancy on apoptosis and the underlying signal transduction pathway. 24 healthy women hi the first-trimester pregnancy were randomly divided into four groups: control group (0-min), experimental groups (10-min, 20-min, 30-min). According to different times, the site of the attached embryo was exposed to a fixed beam from transvaginal ultrasound with a 5.0-MHz tranducer. The chorionic villiobtained 4h after exposure. DNA fragmentation was measured by 1.5% agarose gel electrophoresis. Activation of caspase-3 and cytochrome C release were analyzed by western blotting. Clean bands represented DNA fragmentation occurred after transvaginal ultrasound exposure in 10-min, 20-min and 30-min groups. In contrast with the Omin- and lOmin- groups, cleavage products of active caspase-3 and cytochrome C release significantly increased in 20-min and 30-min groups in a time-dependent manner. We show that exposure to transvaginal ultrasound activates effector caspase-3 mediated apoptotic cascade of chorionic villi in the first-trimester pregnancy. This occurs through the intrinsic death pathway involving in mitochondria! cytochrome c release. Our findings provide a molecular rationale for discriminate use of transvaginal ultrasound at the early stage of pregnancy.
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