Effects of Endothelin and Relaxin on Rat Uterine Segment Contractility1

Abstract

In order to determine the effects of endothelin (ET) and relaxin on uterine contractility, immature female rats were treated with estrogen (E, 1 microgram s.c., Days 1-3) or estrogen and progesterone (2 mg s.c. [E + P], Days 2 and 3), and killed; the uterine horns were removed and suspended in muscle baths. Initially, we determined the contractile response to varying doses of ET and how this response was altered by pretreatment with progesterone. Uterine strips from animals treated with E + P (n = 10) were less sensitive to the stimulatory effects of ET than were strips from E-treated animals (n = 10). This difference was significant at ET doses above 2.5 nM. After completion of the dose-response studies, contractile patterns in response to ET and relaxin were then studied in animals treated with E (n = 10) or E + P (n = 9). ET (5 nM) significantly increased uterine contractility, mostly through an effect on the frequency of contractions (p less than 0.01). Relaxin (25 ng/ml) decreased contractility, affecting all contractile parameters measured (p less than 0.01). ET stimulated contractility in uterine horn segments previously inhibited by relaxin (p less than 0.01), and relaxin reduced the increased contractility produced by earlier exposure to ET (p less than 0.01). These data indicate that ET and relaxin can interact reversibly to control contractility in uterine horn segments in vitro, and that progesterone pretreatment can diminish the contractile response to the stimulatory effects of ET.

Oestrogen-dependent expression of LH/hCG receptors in pig Fallopian tube and their role in relaxation of the oviduct

“…Two basic mechanisms are involved in this transport: the beat of cilia and the waves of smooth muscle activity in the myosalpinx (Hunter, 1988). Many studies show that ovarian steroid hormones (Hunter, 1988;Ayad et al, 1994), the autonomie nervous system (Rodriquez-Martinez, 1984;Kaleczyc, 1994), prostaglandins (Spilman, 1974;Borda et al, 1980;Rodriquez-Martinez and Einarsson, 1985) and endothelin (McGovern et al, 1992;Rosseli et al, 1994) are involved in control of oviductal function. Hunter (1984) suggested that ovulation can somehow co-ordinate the transport of gametes in the pig oviduct to the ampullar-isthmic junction.…”

Endothelin Stimulation of Rat Uterine Segment Contractility Is Estrogen-Dependent

“…The methods used in this study were similar to those described in previously published protocols [11][12][13][14][15]. Experimental animals were maintained at the animal care facility at New Jersey Medical School; their treatment followed guidelines approved by the American Association for Accreditation of Laboratory Animal Care.…”

“…Immature, female Long Evans rats, 22 days of age, were treated with subcutaneous injections of either 1 Ìg estradiol benzoate (Sigma Chemical, St. Louis, Mo., USA) in 0.2 ml sesame oil or 0.2 ml sesame oil as a vehicle control for 3 days. The timing and doses of estradiol benzoate administration followed well-established protocols used previously in our laboratory to study the effects of relaxin and various steroid and peptide hormones on uterine contractility [11][12][13][14][15]. The animals were killed by cervical dislocation on day 4.…”

“…Uterine segments from the estrogen-treated group (n = 16) and those from the vehicle-treated group (n = 18) were used to test the contractile response to endothelin at doses of 5 or 100 nM (endothelin 1; Cambridge Research Biochemicals, Valley Stream, N.Y., USA). The 5-nM dose represents a dose that consistently produced contractions in previously performed studies using the same in vitro system [11]. Baseline contractions were recorded for 15 min.…”

Endothelin production by bovine oviduct epithelial cells

“…2) (Emori et al, 1989). This observation is in agreement with a previous report, in which treatment of cultured vascular endothelial cells by A23187 also induced endothelin produc¬ tion (Boulanger and Lüscher, 1990 (Ecónomos et ., 1992); and in the uterus, the contraction in response to endothelin can be reduced by treating the uterine segments with progesterone (McGovern et al, 1992).…”