To examine whether RU486, an anti-progestogen, is effective in achieving softening and dilatation of the uterine cervical canal, we studied changes of wet weight, dilatation, and extensibility as well as collagenase activity of the cervical canal after the administration of RU486 (5.0mg/kg), 1.0mg estriol (E
3) or 4.0mg dehydroepiandrosterone sulfate (DHA-S) to pregnant rats at 16 days gestation. Serum levels of progesterone (P) and oxytocin (Oxy) were measured with corresponding radioimmunoassays.
The increases of wet weight, dilatation, and extensibility of the cervical canal in RU486-treated rats (16 days gestation) were not different from those in E3 and DHA-S-treated rats.
There was no significant change of collagenase activity in the three differently treated groups. After RU486 administration, P level in serum decreased, but Oxy level did not increase.
These results demonstrate that RU486 was effective in promoting cervical dilatation and in simultaneous-ly softening the cervical canal, without inducing uterine contractions or increasing serum oxytocin concentration.
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