title: Effects of human chorionic gonadotrophin on contractile activity of steroid-primed pig myometrium in vitro.
abstract: We examined the effects of (a) oestrogen and progesterone on concentrations of luteinizing hormone/human chorionic gonadotrophin (LH/hCG) receptors in uterine smooth muscle in vivo and (b) hCG on spontaneous myometrial contractions in vitro. Ovariectomized gilts received 2 ml corn oil (control; n = 5), 2 mg oestradiol benzoate (n = 6) or 20 mg progesterone (n = 5) for 5 days. Gilts were hysterectomized 8 h after the last injection and longitudinal sections of myometrium were incubated in modified Krebs' solution with 0 or 10 i.u. of hCG (n = 10/gilt) for 4 h at 37 degrees C in 95% O2:5% CO2. After incubation, myometrial sections were placed in a tissue chamber perfused with Krebs' solution and mechanical activity was recorded for 30 min. Cell membrane fractions were prepared from myometrial tissue not used for in-vitro studies and analysed for LH/hCG receptors. Treatment with oestradiol benzoate increased (P less than 0.01) the number of LH/hCG-binding sites compared with gilts receiving corn oil or progesterone. Incubation of myometrium with hCG reduced (P less than 0.01) the frequency and amplitude of spontaneous uterine contractions in gilts treated with oestradiol benzoate. In contrast, hCG had no effect (P greater than 0.05) on the pattern of myometrial contractions in gilts given corn oil or progesterone. These results indicate that oestradiol promotes the synthesis of LH/hCG receptors in pig myometrium and incubation of oestrogen-primed tissue with hCG has a quiescent effect on myometrial contractility.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
authors.forename: B
authors.initials: B
authors.lastname: Flowers
authors.forename: A J
authors.initials: AJ
authors.lastname: Ziecik
authors.forename: E V
authors.initials: EV
authors.lastname: Caruolo
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000097:blood; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism; D010052:Ovariectomy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology; D011967:Receptors, Gonadotropin / Q000187:drug effects; D013552:Swine; D014590:Uterine Contraction / Q000187:drug effects*
chemical_list: D006063:Chorionic Gonadotropin; D011967:Receptors, Gonadotropin; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone