153 In vitro effects of endothelin-1 on the contractility of myometrium obtained from pre- and postmenopausal women E Domali1,2, E Asprodini3, P A Molyvdas2 and I E Messinis1 1Department of Obstetrics and Gynecology, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, Greece 2Department of Physiology, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, Greece 3Department of Pharmacology, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, Greece (Requests for offprints should be addressed to I E Messinis) Abstract This study was conducted to evaluate the responsiveness of (2·80·5 g, n=6), the AUC (24·73·3 gmin, n=6), human nonpregnant myometrium to endothelin 1 (ET1) as well as the basal tone (183·621%, n=6) compared (1010 M-106 M) and KCl (80 mM) in relation to the with the two premenopausal groups. In all three groups hormonal profile of the women, who were allocated into KCl exposure induced an initial rise (mean amplitude three groups: group 1, premenopausal follicular phase, value: 1·1 g) followed by a relaxation phase to the primal n=14, group 2, premenopausal luteal phase, n=20, and baseline level (mean duration value: 12 min). Addition of group 3, postmenopausal women, n=12. At a concen- ET1 (106 M) to KCl (80 mM) induced a similar pattern tration of 106 M, ET1 in both groups 1 and 2 induced of contractility to that evoked by ET1 alone which, very low ripples of high frequency (group 1: 8014%, compared with KCl alone lasted significantly longer n=5, group 2: 31463%, n=11; P<0·05 compared with (P<0·05) in all three groups (group 1: 202 min, n=6; the pretreatment frequency) which lasted significantly group 2: 232 min, n=6; group 3: 353 min, n=5). In longer in group 2 (292 min, n=10, P<0·05) than group 3, the percentage change in basal tone was signifi- in group 1 (202 min, n=5), increasing the basal tone cantly smaller following KCl than after the combination of (group 1: 57·96%, n=5, group 2: 64·44%, n=6), KCl plus ET1 (14916%, n=5; P<0·01), indicating a the amplitude of myometrial contractility (group 1: different mechanism of contractility between KCl and 1·20·07 g, n=5, group 2: 1·60·1 g, n=7, P<0·05) ET1. These results demonstrate for the first time differ- and the area under the contractility curve (AUC; group 1: ences in myometrial response to ET1 between pre- and 8·41·1 gmin, n=6, group 2: 11·91·6 gmin, postmenopausal women. It is suggested that KCl and ET1 n=11). In group 3, ET1 (106 M) created a sustained affect uterine contractility through different mechanisms long-lasting contraction (initial phase: 436 min, n=6) and that ovarian steroids may play a regulatory role in characterized by the complete obliteration of spontaneous human uterine responsiveness to ET1. contractility with no ripples at all, and increasing signifi- Journal of Endocrinology (2001) 168, 153–162 cantly (P<0·05) the amplitude of myometrial contractility Introduction are members of the G-protein-linked receptor superfamily (Masaki et al. 1994); ET1 is a selective ligand for ETA Endothelins (ETs) consist of a family of three sarafotoxin- receptor (ET1>ET2), whereas the three peptides, ET1, like peptides ET1, ET2 and ET3 originally isolated from ET2 and ET3 have been reported to display equal affinity the supernatant of cultured porcine endothelial cells for ETB receptor (ET1=ET2=ET3) (Arai et al. 1990, (Yanagisawa et al. 1988). They are produced by different Sakurai et al. 1990, 1992, Bacon et al. 1995). cell types, endothelial and epithelial cells (Ohkubo et al. In particular, the 21-amino acid peptide, ET1, is a 1990, Sakurai et al. 1991, Kamada et al. 1992) and are potent, long-acting vasoconstrictor and proliferative primarily described for their potent vasoconstrictor actions agent produced by a wide range of human cell types (Davenport et al. 1990, Bodelsson et al. 1996, Elchalal & (Sunnergen et al. 1990, Marciniak et al. 1992, Casey & Schenker 1997). It has also been reported that ETs MacDonald 1996) and plays a functional role in the female modulate the contractility in a variety of tissues. The reproductive system (Kamada et al. 1993, Haq et al. 1996, effects of ETs are mediated through two cloned and Apa et al. 1998). Northern blot analysis demonstrated the sequenced subtypes of receptors, ETA and ETB, which release of ET1 by human decidual cells in early pregnancy Journal of Endocrinology (2001) 168, 153–162 Online version via http://www.endocrinology.org 0022–0795/01/0168–153 2001 Society for Endocrinology Printed in Great Britain Downloaded from Bioscientifica.com at 09/24/2021 05:24:41PM via free access 154 E DOMALI and others · Endothelin in human nonpregnant uterus (Kubota et al. 1992) and the presence of immunoreactive from the first day of their last menstrual period, and from prepro ET1 and prepro ET1 mRNA in human endo- serum progesterone and estradiol concentrations measured metrial tissue (Economos et al. 1992, Salamonsen et al. by enzyme linked fluorescent assay (ELFA) in peripheral 1992, Cameron et al. 1992, 1993, Marsh et al. 1994). It has blood samples obtained early in the morning of the day been reported that the binding sites for ET1 are distributed of the operation (means...); group 1: premeno- in the human uterus throughout the menstrual cycle pausal women in the follicular phase, mean estradiol (O’Reilly et al. 1992) and that both subtypes of receptors value 222·442 pmol/l, mean progesterone value are localized in human myometrium, where ETA binding 1·70·1 nmol/l (age: 40–45 years, n=14); group 2: sites represent the principal subtype (Schiff et al. 1993, premenopausal women in the luteal phase, mean estradiol Breuiller-Fouche et al. 1994, Pekonen et al. 1994, Wolff value 653·5141 pmol/l, mean progesterone value et al. 1996). It has been demonstrated that in human 57·131 nmol/l (age: 40–45 years, n=20); group 3: nonpregnant myometrium, ET1 induces contractions postmenopausal women, estradiol value <87·2 pmol/l, (Word et al. 1990, Fried et al. 1993, Svane et al. 1993) progesterone value <1·3 nmol/l (age: 65–70 years, n=12). activating exclusively the ETA receptors, and increasing the two phases of spontaneous myometrial contractility, the phasic and the tonic phase, despite the lesser sensitivity Experiments of nonpregnant compared with pregnant myometrium The experiments were performed and completed within (Word et al. 1991, Osada et al. 1997). Although binding the first 10 h after the removal of the uterus from the studies have shown that ET1 exhibits affinity for ETB abdomen, most usually within the first 6–7 h. The receptors, activation of ETB sites, using ETB selective viability of the tissue under investigation was confirmed ligands, has not been reported to mediate any contractile by the responsiveness of human myometrium to KCl effect on human myometrial tissue; the lack of any (80 mM) at the end of each experiment. The specimens contractile effect on human nonpregnant uterus has been were immediately dissected into longitudinal strips of attributed to the small population of ETB receptors (less 521 mm parallel to the muscle fiber orientation. than 25%) on human myometrium, or to their involve- Briefly, the strips were mounted horizontally in bathing ment in mechanisms of relaxation and proliferation; the chambers for isometric recording with one end fixed and precise role of ETB subtypes of receptors in human uterus the other attached to an isometric transducer connected to needs to be further elucidated (Maggi et al. 1994, Bacon an amplifier. An initial resting tension of 1 g was applied to et al. 1995, Heluy et al. 1995, Wolff et al. 1996, Osada each strip. The tissues were continuously perfused with et al. 1997). However, in none of these studies has the Krebs’ solution at 37 C, gassed with 95% O2 and 5% ff e ect of ET1 on myometrial contractility been examined CO2. Tension generated by the muscle strips was recorded specifically in relation to the hormonal profile of the on a GRASS FTO3C. force displacement transducer and women. Knowing that human uterus is a target organ of displayed on a universal oscillograph (Harvard) recorder. sex steroids, the purpose of our study was to elucidate the During the experiments, the strips were allowed to effect of ET1 on human uterine contractility in relation to equilibrate for 1 to 2 h until the spontaneous contractility the sex steroid milieu of the women, and to determine became regular in frequency and intensity. The tissues possible alterations in premenopausal women (follicular were then exposed to the various stimuli for 7 min, and or luteal phase of the normal menstrual cycle) and in washed out with Krebs’ solution. The duration of the drug postmenopausal women. application in our experimental procedure was dictated by two factors: first, the time required for the superfusing solution to reach steady-state concentration within the Materials and Methods bath, and secondly the high cost of ET1. Therefore, the 7-min application period used in our experiments was Specimens considered a satisfactory period of time to ascertain the Myometrial tissue was collected from women undergoing achievement of the full effect of the drug, and at the same hysterectomy for benign gynecological disorders. Informed time to limit the cost of the experiment. Two types of consent was obtained. All women were operated on under experiment were performed. In the first series of exper- the same conditions in terms of premedication and anes- iments five different concentrations of ET1 (10 10 M, thetic drugs.