Background: Pre-term birth is a major health care challenge throughout the world, and preterm labor represents a potentially reversible component of this problem. Current tocolytics do not improve preterm labor beyond 48 h. We have previously shown that anoctamin 1 (ANO1) channel blockade results in relaxation of pre-contracted human uterine smooth muscle (USM). Three drug classes with reported medicinal effects in humans also have members with ANO1 antagonism. In this study, we compared the ability of representatives from these 3 classes to reduce human USM contractility and excitability. Objective: This study sought to examine the comparative potency of 3 ANO1 antagonists on pregnant human USM relaxation, contraction frequency reduction, inhibition of intracellular calcium release and membrane hyperpolarization. Methods: Experiments were performed using: 1) Ex vivo organ bath (human pregnant tissue), 2) Oxytocin-induced calcium flux (in vitro human USM cells) and 3) Membrane potential assay (in vitro human USM cells). Results: Benzbromarone (BB) demonstrated the greatest potency among the compounds tested with respect to force, frequency inhibition, reducing calcium elevation and depolarizing membrane potential. Conclusion: While all 3 ANO1 antagonists attenuate pregnant human uterine tissue contractility and excitability, BB is the most potent tocolytic drug. Our findings may serve as a foundation for future structure-function analyses for novel tocolytic drug development.
Object We aimed to identify the β-adrenoceptor (β-AR) subtypes involved in isoprenaline-induced relaxation of guinea pig colonic longitudinal smooth muscle using pharmacological and biochemical approaches. Methods Longitudinal smooth muscle was prepared from the male guinea pig ascending colon and contracted with histamine prior to comparing the relaxant responses to three catecholamines (isoprenaline, adrenaline, and noradrenaline). The inhibitory effects of subtype-selective β-AR antagonists on isoprenaline-induced relaxation were then investigated. Results The relaxant potencies of the catecholamines were ranked as: isoprenaline > noradrenaline ≈ adrenaline, whereas the rank order was isoprenaline > noradrenaline > adrenaline in the presence of propranolol (a non-selective β-AR antagonist; 3 × 10−7 M). Atenolol (a selective β1-AR antagonist; 3 × 10−7–10−6 M) acted as a competitive antagonist of isoprenaline-induced relaxation, and the pA2 value was calculated to be 6.49 (95% confidence interval: 6.34–6.83). The relaxation to isoprenaline was not affected by ICI-118,551 (a selective β2-AR antagonist) at 10−9–10−8 M, but was competitively antagonized by 10−7–3 × 10−7 M, with a pA2 value of 7.41 (95% confidence interval: 7.18–8.02). In the presence of propranolol (3 × 10−7 M), the relaxant effect of isoprenaline was competitively antagonized by bupranolol (a non-selective β-AR antagonist), with a pA2 value of 5.90 (95% confidence interval: 5.73–6.35). Conclusion These findings indicated that the β-AR subtypes involved in isoprenaline-induced relaxation of colonic longitudinal guinea pig muscles are β1-AR and β3-AR.
Object We identified the β-adrenoceptor (β-AR) subtypes responsible for the relaxant responses to adrenaline (AD) and noradrenaline (NA) in the rat thoracic aorta and examined the role of cAMP which is involved in these relaxant responses. Methods The effects of β-AR antagonists or the adenylyl cyclase inhibitor SQ 22,536 on AD- and NA-induced relaxant responses in phenylephrine-induced contraction and increases in cAMP levels were examined in isolated, endothelium-denuded rat thoracic aorta segments. Results AD-induced relaxation was completely suppressed by propranolol (10−7 M) or by ICI-118,551 (10−8 M) plus atenolol (10−6 M), and was also very strongly inhibited by ICI-118,551 (10−8 M) alone. AD (10−5 M) increased tissue cAMP levels by approximately 1.9-fold compared with that in non-stimulated aortic tissue, but did not significantly increase cAMP levels in the presence of ICI-118,551 (10−8 M) or SQ 22,536 (10−4 M). AD-induced relaxation was strongly suppressed by SQ 22,536 (10−4 M). NA-induced relaxation was almost completely suppressed by atenolol (10−6 M) plus ICI-118,551 (10−8 M) although it was hardly affected by ICI-118,551 (10−8 M) alone. NA (10−5 M) increased tissue cAMP levels by approximately 2.2-fold compared with that in non-stimulated aortic tissue, but did not significantly increase cAMP levels in the presence of atenolol (10−6 M) or SQ 22,536 (10−4 M). NA-induced relaxation was strongly suppressed by SQ 22,536 (10−4 M). Conclusion In rat thoracic aorta, AD- and NA-induced relaxations, which are both strongly dependent on increased tissue cAMP levels, are mainly mediated through β2- and β1-adrenoceptors respectively.
EXPEPIMENTAL AND CLINICAL STUDIES ON LOWER ESOPHAGEAL SPHINCTER MOTOR FUNCTION WITH SPECIAL REFERENCE TO THE INFLUENCE OF VAGAL DENERVATION
Released: July 21, 2010 | Volume 30 Pages 97-110
Sadanobu ABE
Views: 62
Human resistin in cardiovascular disease
Released: April 14, 2012 | Volume 48 Pages 27-35
Sang Eun Lee, Hyo-Soo Kim
Views: 62
THE CONTROL OF SMOOTH MUSCLE TISSUES BY NONADRENERGIC NONCHOLINERGIC (NANC) NERVE FIBRES IN THE AUTONOMIC NERVOUS SYSTEM
Released: July 21, 2010 | Volume 31 Pages 67-78
Hiroyuki ITOH, Jirou SAKAI, Akihiko IMOTO, Kate E. CREED
Views: 60
AN EXPERIMENTAL STUDY OF THE DIURNAL CHANGES IN COLONIC MOTILITY CENTERING ON DEFECATION
Released: July 21, 2010 | Volume 28 Pages 15-24
Yasumitsu KATSUURA
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INTRAOCULAR SMOOTH MUSCLE PHYSIOLOGY RELATING TO PATHOGENESIS AND THERAPY OF GLAUCOMA
Released: July 21, 2010 | Volume 32 Pages 175-194
Ryo SUZUKI
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