OBJECTIVETo study the effect of mifepristone on the expression of chorionic gonadotropin beta subunit (beta-CG) and collagen type IV in female Rhesus monkey decidua and villus during the first trimester of pregnancy.

METHODSEighteen sexually mature female Rhesus monkeys were allowed to cohabitate with their male counterparts and diagnosed as being pregnant by B-ultrasound at days 38-45 of the menstrual cycle. They were randomly divided into mifepristone treatment group (15 mg/ml.kg.day, 3 days), control group(no treatment) and CMC-Na treatment group(0.5% CMC-Na, 1 ml/kg.day, 3 days). The content and distribution of chorionic gonadotropin beta subunit and collagen type IV in the female Rhesus monkeys were examined by immunohistochemical technique.

RESULTSCompared with the control group, the immunohistochemical reaction intensity of chorionic gonadotropin beta subunit in the plasm of stroma cells, glandular epithelial cells and decidual cells of decidua, and synctial trophoblast cells of villus significantly decreased in the mifepristone treatment group. The positive staining of collagen type IV surrounding the epithelial glandular basal membrane, decidual cells and blood vessels in decidua and surrounding the synctial trophoblast cells in villus were significantly reduced.

CONCLUSIONMifepristone may have a strong effect in decreasing the bioactivity of beta-CG in decidua and the synthesis of beta-CG in villus, and in accelerating the degradation of collagen type IV in decidua and villus.