RESUMEN
The molecular mechanisms regulating human uterine quiescence and parturition are poorly understood. Potassium channels are central to regulation of cell membrane potential and contractility of smooth muscle. The aim of this study was to examine the expression of ATP-sensitive potassium channel (K(ATP) channel) subunits in human myometrium, and to investigate for possible differential expression of these subunits in myometrium obtained from three different functional states: (i) non-pregnant (NP); (ii) late pregnant not in labour (PNL); and (iii) late pregnant in labour (PL). RT-PCR detected the presence of mRNA for four subunits of K(ATP) channels (Kir6.1, Kir6.2, SUR1 and SUR2B) in the three tissue types. Quantitative analysis of these subunits was achieved with real-time RT-PCR using Lightcycler(TM) technology. This analysis showed that there were significantly higher levels of Kir6.1 and SUR2B transcripts in NP myometrium compared with those measured in myometrium obtained during pregnancy (P < 0.001). Lower levels of Kir6.2 and SUR1 mRNA expression were found, although higher transcript levels in NP myometrium (P < 0.05) were still observed. Our results indicate that the major K(ATP) channel expressed in human myometrium is composed of Kir6.1 and SUR2B, and that down-regulation of this channel may facilitate myometrial function during late pregnancy.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Adenosina Trifosfato/metabolismo , Miometrio/fisiología , Canales de Potasio/genética , ARN Mensajero/metabolismo , Adulto , Femenino , Regulación de la Expresión Génica , Humanos , Trabajo de Parto , Canales de Potasio/metabolismo , Canales de Potasio de Rectificación Interna/genética , Canales de Potasio de Rectificación Interna/metabolismo , Embarazo , Receptores de Droga/genética , Receptores de Droga/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Receptores de Sulfonilureas , Transcripción GenéticaRESUMEN
There is little information outlining the role of Rho kinase, RhoA, and calcium sensitization in regulation of human uterine contractility during pregnancy. The aims of this study were to investigate the expression of RhoA, and the Rho kinases ROCK I and ROCK II in human pregnant myometrium, to evaluate the effects of Rho kinase inhibition on pregnant human myometrial contractility in vitro, and to compare these effects with those of the calcium channel blocker nifedipine. RT-PCR using primers for RhoA, ROCK I and ROCK II was performed on mRNA isolated from human pregnant myometrium. Isometric recording was performed in isolated myometrial strips obtained at Caesarean section. The effects of the Rho kinase inhibitor Y-27632 (1 nmol/l to 10 mmol/l), and nifedipine (1 nmol/l to 10 mmol/l), on oxytocin (0.5 nmol/l) induced contractions were measured and compared. Expression of RhoA, ROCK I and ROCK II mRNA was identified in human pregnant myometrium (n = 3). Y-27632 exerted a potent relaxant effect on myometrial contractility with a pD(2) value (+/- SEM) of 7.63 +/- 0.38 (n = 6). The maximum net relaxant effect (+/- SEM) was 72.3 +/- 6.1% (n = 6). Corresponding values for nifedipine were 7.24 +/- 0.48 (n = 6; P = 0.469) and 93.40 +/- 3.1% (n = 6; P = 0.028). Rho A/Rho kinase-mediated calcium sensitization may play role in the physiology of human parturition, and pharmacological inhibition of this pathway may therefore provide a novel approach to tocolysis for pre-term labour.
Asunto(s)
Miometrio/metabolismo , Proteínas Serina-Treonina Quinasas/biosíntesis , Adulto , Amidas/farmacología , Bloqueadores de los Canales de Calcio/farmacología , Inhibidores Enzimáticos/farmacología , Femenino , Expresión Génica , Humanos , Péptidos y Proteínas de Señalización Intracelular , Nifedipino/farmacología , Embarazo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/genética , Piridinas/farmacología , Quinasas Asociadas a rho , Proteína de Unión al GTP rhoA/metabolismoRESUMEN
OBJECTIVE: To compare the effects of three cyclooxygenase-2 (COX-2) inhibitors: nimesulide, meloxicam, and celecoxib, which exhibit varying COX-2 selectivity, on contractile activity in pregnant (before and after labor) and nonpregnant human myometrial tissue in vitro. METHODS: Isometric tension recording was performed under physiologic conditions in isolated myometrial strips obtained from 33 women undergoing hysterectomy or either elective or emergency cesarean section. The effects of cumulative additions of nimesulide, meloxicam, and celecoxib (between 1 nmol/L and 100 micromol/L) on myometrial contractility were measured, and values for -log(10) EC(50) and mean maximal inhibition were compared. RESULTS: Nimesulide, meloxicam, and celecoxib exerted significant relaxant effects on contractility in nonpregnant, pregnant nonlabor, and pregnant labor myometrial strips. Values for -log(10) EC(50) values (+/- standard error of the mean) were as follows: nimesulide (nonpregnant) 5.14 +/- 0.93 (n = 6), (pregnant nonlabor) 4.91 +/- 0.75 (n = 6), and (pregnant labor) 5.84 +/- 0.35 (n = 6); meloxicam (nonpregnant) 6.53 +/- 0.57 (n = 6), (pregnant nonlabor) 4.80 +/- 0.71 (n = 6), and (pregnant labor) 5.62 +/- 0.21 (n = 6); celecoxib (nonpregnant) 6.15 +/- 0.99 (n = 6), (pregnant nonlabor) 7.08 +/- 0.98 (n = 6), and (pregnant labor) 7.25 +/- 0.99 (n = 3). Celecoxib exhibited greater potency than nimesulide or meloxicam (P < .01). The range of maximal relaxation values achieved in the three tissue types were as follows: nimesulide 68-70% (n = 18; P < .01), meloxicam 69-84% (n = 18; P < .01), and celecoxib 69-77% (n = 15; P < .01). CONCLUSION: COX-2 inhibitors exert significant relaxation in human myometrium with a similar potency in nonpregnant and pregnant (before and after labor onset) tissues. Celecoxib, a COX-2 specific inhibitor, was more potent than nimesulide or meloxicam, COX-2 preferential inhibitors.
Asunto(s)
Inhibidores de la Ciclooxigenasa/farmacología , Isoenzimas/antagonistas & inhibidores , Miometrio/efectos de los fármacos , Sulfonamidas/farmacología , Tiazinas/farmacología , Tiazoles/farmacología , Contracción Uterina/efectos de los fármacos , Adulto , Celecoxib , Cesárea , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Femenino , Humanos , Histerectomía , Trabajo de Parto , Meloxicam , Proteínas de la Membrana , Persona de Mediana Edad , Embarazo , Prostaglandina-Endoperóxido Sintasas , PirazolesRESUMEN
OBJECTIVE: 1. To investigate the effects of the selective beta-3 adrenoreceptor agonist, BRL 37344, on human pregnant myometrial contractility in vitro. 2. to compare these effects with those of the beta-2 adrenoreceptor agonist, ritodrine. METHODS: Isometric tension recording was performed under physiological conditions in isolated myometrial strips from biopsies obtained at elective caesarean section. Following pre-incubation with oxytocin (10(-9) M), the effects of cumulative additions of BRL 37344 or ritodrine (10(-8)-10(-3.5) M) on myometrial contractility were investigated. Results were expressed as -log EC50 (pD2) and mean maximal inhibition achieved for both drug compounds. RESULTS: BRL 37344 exerted a concentration dependant relaxant effect on myometrial contractions in all strips exposed [pD2, 7.26 (0.48) (SEM); mean maximal inhibition 61.98 (4.89%); n = 6]. Similarly, ritodrine exerted a concentration dependant inhibition of myometrial contractility in all strips exposed [pD2 = 7.40 (0.28); mean maximal inhibition 59.49 (3.97%); n = 6]. There was no significant difference between calculated pD2 values (P = 0.65) or mean maximal inhibition achieved (P = 0.79). CONCLUSIONS: The beta-3 adrenoreceptor agonist BRL 37344 induced relaxation of human myometrial contractions with similar potency to that of the most commonly used tocolytic agent ritodrine. This raises the possibility that the novel beta-3 adrenoreceptor agonists may have potential as therapeutic agents for human preterm labour. In view of their reported reduced cardiovascular side effects their potential clinical use requires further evaluation.