HUMAN MYOMETRIAL CHORIONIC-GONADOTROPIN LUTEINIZING-HORMONE RECEPTORSIN PRETERM AND TERM DELIVERIES

Nonpregnant human myometrium contains functional hCG/LH receptors. The present study investigated whether pregnant human myometrium also con tains these receptors and whether they vary as a function of delivery in preterm or term pregnancies. Northern blotting revealed that pregna nt human myometrium contains 4.3- and 2.2-kilobase receptor messenger ribonucleic acid transcripts. Immunoblotting with a specific hCG/LH re ceptor antibody showed that myometrium contains 70- and SD-kilodalton immunoreactive proteins. Ligand blotting demonstrated that only the 50 -kilodalton protein could bind [I-125]hCG, and this binding was inhibi ted by excess unlabeled hCG. In situ hybridization and immunocytochemi stry revealed that the receptor messenger ribonucleic acid and recepto r protein are present in myometrial and vascular smooth muscle. The my ometrial smooth muscle receptor levels were lower during labor compare d to those before labor at preterm and term pregnancy. In summary, our study demonstrates that pregnant human myometrium express hCG/LH rece ptor gene. The receptor levels were lower during labor compared to tho se before labor in preterm or term pregnancy. These data suggest that hCG, via its receptors, may contribute to myometrial quiescence until labor begins at the end of pregnancy.