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Isometric Tension (isometric + tension)
Terms modified by Isometric Tension Selected AbstractsCaffeine administration results in greater tension development in previously fatigued canine muscle in situEXPERIMENTAL PHYSIOLOGY, Issue 6 2005Richard A. Howlett In isolated single skeletal myocytes undergoing long-term fatiguing contractions, caffeine (CAF) can result in nearly immediate restoration of generated tension to near-prefatigue levels by increasing Ca2+ release via activation of sarcoplasmic reticulum release channels. This study tested whether arterial CAF infusion (>5 mm) would cause a similar rapid restoration of tetanic isometric tension during contractions to fatigue in perfused canine hindlimb muscle in situ. Tetanic contractions were elicited by electrical stimulation (200 ms trains, 50 Hz, 1 contraction s,1), and biopsies were taken from the muscle at rest and during contractions: (1) following the onset of fatigue (tension ,60% of initial value); and (2) following CAF administration. Resting muscle ATP, PCr and lactate contents were 25.2 ± 0.4, 76.9 ± 3.3 and 14.4 ± 3.3 mmol (kg dry weight),1, respectively. At fatigue, generated tetanic tension was 61.1 ± 6.9% of initial contractions. There was a small but statistically significant recovery of tetanic tension (64.9 ± 6.6% of initial value) with CAF infusion, after which the muscle showed incomplete relaxation. At fatigue, muscle ATP and PCr contents had fallen significantly (P < 0.05) to 18.1 ± 1.1 and 18.9 ± 2.1 mmol (kg dry weight),1, respectively, and lactate content had increased significantly to 27.7 ± 5.4 mmol (kg dry weight),1. Following CAF, skeletal muscle ATP and PCr contents were significantly lower than corresponding fatigue values (15.0 ± 1.3 and 10.9 ± 2.2 mmol (kg dry weight),1, respectively), while lactate was unchanged (22.2 ± 3.9 mmol (kg dry weight),1). These results demonstrate that caffeine can result in a small, but statistically significant, recovery of isometric tension in fatigued canine hindlimb muscle in situ, although not nearly to the same degree as seen in isolated single muscle fibres. This suggests that, in this in situ isolated whole muscle model, alteration of Ca2+ metabolism is probably only one cause of fatigue. [source] The neuronal and endothelium-dependent relaxing responses of human corpus cavernosum under physiological oxygen tension last longer than previously expectedINTERNATIONAL JOURNAL OF UROLOGY, Issue 5 2004KAZUNORI KIMURA Abstract Background: Intracavernosal oxygen tension varies greatly in the process of erection. Blood extracted from the human penis demonstrates an increase from approximately 30 mmHg Po2 in the flaccid state to 100 mmHg in the erect state of the penis. In the present study, using these levels as a guide, we investigate how the NO-dependent relaxation of human corpus cavernosum changed under physiological oxygen tensions ranging from approximately 30 to 100 mmHg. Methods: Human penile tissue specimens were obtained at penile surgery with informed consent from the patients. The preparations were mounted in Krebs solution in an organ bath and the isometric tension was recorded. Krebs solutions of various oxygen tensions were prepared by bubbling 5% CO2 in N2 and O2. The NO-dependent relaxation caused by electrical field stimulation (EFS) and acetylcholine (ACh) was studied, and the amplitude and duration of relaxation evaluated. Results: The amplitude of relaxation induced by EFS was significantly decreased under physiological oxygen tension conditions (P < 0.01). The duration of the relaxant response induced by EFS and ACh was significantly prolonged in physiological oxygen tension conditions than in high oxygen tension (P < 0.01). However, there was no correlation between the duration of relaxation induced by EFS and each physiological oxygen tension level. The duration of relaxation induced by ACh was most prolonged at 60,69 mmHg oxygen tension. Conclusion: Physiologically, the effect of NO may last longer than was previously thought. In addition, it would seem that there is an optimal physiological oxygen tension for maximum ACh-induced relaxation. [source] Effect of human chorionic gonadotrophin on in vitro contractions of stimulated detrusor muscle strips of female ratsJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 5 2009Diaa E. E. Rizk Abstract Aims:, We studied the effect of human chorionic gonadotrophin (hCG) on the in vitro detrusor muscle contractions in female rats. Methods:, Two adjacent detrusor muscle strips from the bladder dome of 18 female Wistar rats (230,250 gm) were mounted in an organ bath for the recording of isometric tension. Carbachol (10,9,10,3 M), ,,, methylene adenosine 5,-triphosphate (ATP) (10,9,10,3 M) and potassium chloride (KCl) (10,4,10,3 M) were applied (n = 6 × 3 groups). Concentration-response curves, before and after the addition of hCG (100 iu/mL) or oxybutynin (10,5 M) to either muscle strip, were compared. Results:, All curves were displaced to the right by hCG in a concentration-dependent manner with significant inhibition of contractions induced by carbachol (P < 0.001) and KCl (P = 0.016) but not those induced by ,,,-methylene ATP (P = 0.4). Estimated order of potency of inhibition was carbachol>KCl>,,,-methylene ATP. The overall inhibitory effect of hCG was significantly less than oxybutynin (P < 0.001). Conclusions:, hCG significantly inhibited in vitro detrusor contractions induced by depolarization (KCl) and cholinergic (carbachol) but not purinergic (,,,-methylene ATP) stimulation in a dose-dependent manner in female rats. [source] Determinants of force rise time during isometric contraction of frog muscle fibresTHE JOURNAL OF PHYSIOLOGY, Issue 3 2007K. A. P. Edman Force,velocity (F,V) relationships were determined for single frog muscle fibres during the rise of tetanic contraction. F,V curves obtained using isotonic shortening early in a tetanic contraction were different from those obtained at equivalent times with isovelocity shortening, apparently because changing activation early in the contraction leads, in isovelocity experiments, to changing force and changing series elastic extension. F,V curves obtained with isotonic and with isovelocity shortening are similar if the shortening velocity in the isovelocity trials is corrected for series elastic extension. There is a progressive shift in the scaling of force,velocity curves along the force axis during the course of the tetanic rise, reflecting increasing fibre activation. The time taken for F,V curves to reach the steady-state position was quite variable, ranging from about 50 ms after the onset of contraction (1,3°C) to well over 100 ms in different fibres. The muscle force at a fixed, moderately high shortening velocity relative to the force at this velocity during the tetanic plateau was taken as a measure of muscle activation. The reference velocity used was 60% of the maximum shortening velocity (Vmax) at the tetanic plateau. The estimated value of the fractional activation at 40 ms after the onset of contraction was used as a measure of the rate of activation. The rate of rise of isometric tension in different fibres was correlated with the rate of fibre activation and with Vmax during the plateau of the tetanus. Together differences in rate of activation and in Vmax accounted for 60,80% of the fibre-to-fibre variability in the rate of rise of isometric tension, depending on the measure of the force rise time used. There was not a significant correlation between the rate of fibre activation and Vmax. The steady-state F,V characteristics and the rate at which these characteristics are achieved early in contraction are seemingly independent. A simulation study based on F,V properties and series compliance in frog muscle fibres indicates that if muscle activation were instantaneous, the time taken for force to rise to 50% of the plateau value would be about 60% shorter than that actually measured from living fibres. Thus about 60% of the force rise time is a consequence of the time course of activation processes and about 40% represents time taken to stretch series compliance by activated contractile material. [source] The Effect of Korean Red Ginseng Extract on the Relaxation Response in Isolated Rabbit Vaginal Tissue and Its MechanismTHE JOURNAL OF SEXUAL MEDICINE, Issue 9 2008Sun-Ouck Kim MD ABSTRACT Introduction., Ginseng is an herbal medicine with a variety of biological activities. Aim., The purpose of this study was to investigate the effect of Korean red ginseng (KRG) extract on the relaxation response in isolated rabbit vaginal tissue and its mechanism as a potential therapeutic agent for female sexual dysfunction. Method., Strips of rabbit vagina were mounted in organ chambers to measure isometric tension. After the strips were precontracted with phenylephrine, the contractile responses to KRG extract (1,20 mg/mL), nitric oxide inhibitor (N[omega]-nitro-L-arginine methyl ester [L-NAME]), an inhibitor of soluble guanylate cyclase (methylene blue), an inhibitor of Ca2+ -activated K+ channels (tetraethylammonium [TEA]), and an adenosine triphosphate (ATP)-sensitive K+ channel blocker (glybenclamide) were examined. Main Outcome Measures., The relaxation of the vaginal tissue strip was assessed after treating KRG extract or other chemicals. Results., KRG (1,20 mg/mL) extract relaxed the vaginal tissue strip in a dose-dependent manner up to 85%. The relaxation effect was significantly inhibited by L-NAME (30 µM) and methylene blue (30 µM) (P < 0.05). In addition, KRG inhibited the contraction induced by depolarization with 10, 20, and 40 mM KCl. The KRG-induced relaxation effect was significantly inhibited by TEA (300 µM) (P < 0.05), and not by glybenclamide (30 µM). Conclusions., These data show that KRG extract has a relaxing effect on rabbit vaginal smooth muscle tissue. These effects might be mediated partly through the NO pathway and hyperpolarization via Ca2+ -activated K+ channels. Kim S-O, Kim MK, Lee H-S, Park JK, and Park K. The effect of Korean red ginseng extract on the relaxation response in isolated rabbit vaginal tissue and its mechanism. J Sex Med 2008;5:2079,2084. [source] Contractile Changes of the Clitoral Cavernous Smooth Muscle in Female Rabbits with Experimentally Induced Overactive BladderTHE JOURNAL OF SEXUAL MEDICINE, Issue 5 2008Soon-Chul Myung MD ABSTRACT Introduction., Recently, growing clinical evidence has suggested that sexual dysfunction is more prevalent in women with overactive bladder (OAB). Aims., However, there has been no basic research to clarify the relationship between OAB and female sexual dysfunction. Therefore, we investigated this issue using a rabbit model of OAB. Methods., Twenty-seven New Zealand white female rabbits were randomly divided into the OAB and control groups. Main Outcome Measures., The contractile responses of clitoral cavernous strips to K+, phenylephrine (PE), Bay K 8644, and endothelin (ET)-1, and the relaxation responses of acetylcholine (ACh), sodium nitroprusside (SNP), and Y-27632 to PE-induced contraction by measuring isometric tension. Results., The contractile responses to K+, PE, Bay K 8644, and ET-1 were significantly more increased in the OAB group in a dose-dependant manner than in the control group (P < 0.05), and the responses to ET-1 were more prominent than those to the remaining substances (P < 0.01). The increased contractile responses to ET-1 were blocked by BQ123 (ETA receptor antagonist) but not by BQ788 (ETB receptor antagonist). Clitoral cavernosal strips from the OAB group were more difficult to relax than those from the control group in terms of ACh- and SNP-induced relaxation (P < 0.05). The Y-27632-induced relaxant responses to PE- and ET-1-induced contraction were less prominent in the OAB group than in the control group. Conclusions., The results of this study provide evidence that female OAB may deteriorate clitoral engorgement, which is associated with a greater force generation by increased calcium sensitization and subsequently decreased of relaxation. The activation of ET and Rho-kinase system may be crucial to negatively effect the clitoral smooth muscle relaxation in experimentally induced OAB animal model. But whether these vasomotor effects are revived in human clitoris is still debatable. Myung S-C, Lee M-Y, Lee S-Y, Yum S-H, Park S-H, and Kim S-C. Contractile changes of the clitoral cavernous smooth muscle in female rabbits with experimentally induced overactive bladder. J Sex Med 2008;5:1088,1096. [source] The Effect of Ovariectomy on Rat Vaginal Tissue Contractility and HistomorphologyTHE JOURNAL OF SEXUAL MEDICINE, Issue 2 2006F. Fatih Önol MD ABSTRACT Introduction., Ovarian hormones have an important role in age-related genital arousal disorders; however, our knowledge regarding possible vaginal wall morphology and contractility changes in low-hormonal states is limited. Aims., To investigate morphological and functional alterations in the vaginal tissue in a rat ovariectomy model and to show the differences between proximal and distal vagina. Methods., Six weeks following ovariectomy, vaginal tissues were examined under light and electron microscopy. Circularly cut distal and proximal tissues were studied in the organ bath under isometric tension and compared with age-matched controls. Contractile responses to electrical field stimulation (EFS), phenylephrine, carbachol, and the effects of alpha-1 and alpha-2 blockade on EFS-induced contractility were investigated. Relaxation responses to EFS and vardenafil were investigated in precontracted strips. Main Outcome Measures., Differences between control and ovariectomy groups in terms of vaginal tissue contractility and histomorphological properties. Results., Distal vagina showed different epithelial characteristics and a better-developed muscularis compared with proximal vagina. Ovariectomy caused thinning of the epithelium, severe degeneration in epithelial architecture, and smooth muscle atrophy. Contraction and relaxation responses of distal strips were significantly lower in ovariectomized rats. Contractile responses to neuropharmacological stimulation were insignificant in proximal strips of both groups. EFS-induced contractions in distal strips diminished significantly after alpha-1 and alpha-2 adrenergic blockade. EFS caused frequency-dependent relaxation responses in precontracted distal strips, which were significantly decreased after nitric oxide synthase inhibition. Conclusions., Ovariectomy causes significant alteration in rat vaginal tissue morphology and contractility. Contraction and relaxation responses of distal vagina are significantly greater compared with morphologically distinct proximal vagina. Alpha-1 and alpha-2 receptors are the main mediators of contraction in distal rat vaginal tissue whereas nitric oxide pathway may have at least a partial role in relaxation. Main mediators of the rat vaginal tissue relaxation and the effect of ovariectomy on this regulation are yet to be defined. Önol FF, Ercan F, and Tarcan T. The effect of ovariectomy on rat vaginal tissue contractility and histomorphology. J Sex Med 2006;3:233,241. [source] Tamoxifen dilates porcine coronary arteries: roles for nitric oxide and ouabain-sensitive mechanismsBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2006H S Leung Background and purpose: Experiments were designed to determine the mechanism of the relaxation induced by tamoxifen in porcine coronary arteries at the tissue, cellular and molecular levels. Experimental approach: Porcine left circumflex coronary arteries were isolated and isometric tension was measured. [Ca2+]i in native endothelial cells of intact arteries was determined by a calcium fluorescence imaging technique and eNOS ser1177 phosphorylation was assayed by Western blotting. Key results: Tamoxifen induced an endothelium-dependent relaxation that was antagonized by ICI 182,780 and abolished by NG -nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4]oxadizolo[4,3-a]quinoxalin-1-one (ODQ). L-Arginine reversed the effect of L-NAME while indomethacin was without effect. Tamoxifen-induced relaxation was attenuated by charybdotoxin (CTX) plus apamin, ouabain or by incubation in a K+ -free solution. Moreover, tamoxifen triggered extracellular Ca2+ -dependent increases in endothelial [Ca2+]i and this effect was abolished by ICI 182,780. Endothelium-independent relaxation to sodium nitroprusside was also inhibited by ouabain or in a K+ -free solution. Furthermore, tamoxifen increased endothelial nitric oxide synthase (eNOS) phosphorylation at Ser-1177 and ICI 182,780 prevented this effect. Conclusions and Implications: The present results suggest that tamoxifen mainly induces endothelium-dependent relaxation and that endothelial nitric oxide (NO) is the primary mediator of this effect. NO-dependent responses may result from elevated [Ca2+]i in endothelial cells; an effect abolished by ICI 182,780. NO activates Na+/K+ -ATPase in vascular smooth muscle, leading to relaxation. These results suggest that tamoxifen is able to modulate eNOS phosphorylation directly. British Journal of Pharmacology (2006) 149, 703,711. doi:10.1038/sj.bjp.0706921 [source] Adrenergic mechanisms in canine nasal venous systemsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2003Min Wang We investigated the adrenergic mechanisms of the two venous systems that drain the nasal mucosa, thereby their exact role in eliciting nasal decongestion. The action of endogenously released noradrenaline and exogenous adrenergic agonists on different segments of the nasal venous systems, i.e. collecting (LCV, SCV) and outflow (SPV) veins of posterior venous system, collecting (ACV) and outflow (DNV) veins of anterior venous system and venous sinusoids of the septal mucosa (SM), were studied. In vitro isometric tension of the vascular segments was measured. Transmural nerve stimulation (TNS) produced constriction in ACV, DNV and SM, primary constriction followed by secondary dilatation in LCV and SCV and dilatation in SPV. Tetrodotoxin (10,6M) abolished all responses. Phentolamine (10,6M), prazosin (10,6M) and rauwolscine (10,7M) inhibited the constriction in all venous vessels. Propranolol (10,6M), atenolol (10,6M) and ICI 118,551 (10,6M) inhibited the relaxation in SPV but not in LCV and SCV. Phenylephrine and clonidine constricted whereas dobutamine and terbutaline relaxed all venous vessels dose-dependently. These results indicate ,1 -, ,2 -, ,1 - and ,2 -adrenoceptors are present in both venous systems. TNS causes constriction of anterior venous system, venous sinusoids and posterior collecting veins primarily via postjunctional ,2 -adrenoceptors but relaxation of posterior outflow vein equally via postjunctional ,1 - and ,2 -adrenoceptors. The combined action of the two adrenergic mechanisms can reduce nasal airway resistance in vivo by decreasing vascular capacitance and enhancing venous drainage via the posterior venous system. British Journal of Pharmacology (2003) 138, 145,155. doi:10.1038/sj.bjp.0705020 [source] Phosphoinositide 3-kinase mediated signalling contributes to development of diabetes-induced abnormal vascular reactivity of rat carotid arteryCELL BIOCHEMISTRY AND FUNCTION, Issue 1 2006Mariam H. M. Yousif Abstract Diabetes mellitus is associated with vascular complications, including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive agents. Phosphatidylinositol 3-kinase (PI3K) is a signalling enzyme that plays key roles in vascular growth, proliferation and cellular apoptosis and is implicated in modulating vascular smooth muscle contractility. The aim of this study was to determine whether PI3K plays a role in development of diabetes-induced altered vascular reactivity to selected vasoconstrictors and vasodilators. The effect of 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), a selective PI3K inhibitor, on isolated segments of carotid arteries from streptozotocin (STZ)-diabetic rats was investigated. Ring segments of the isolated carotid arteries were mounted in organ baths to measure changes in isometric tension. Our results showed that STZ treatment produced an increase in the vasoconstrictor response to norepinephrine (NE), angiotensin II (Ang II) and endothelin-1 (ET-1) and an attenuated vasodilator response to carbachol and histamine in the isolated carotid arteries from STZ-diabetic animals. Diabetes-induced impaired vascular responsiveness to the vasoactive agonists was prevented by chronic inhibition of PI3K by LY294002 even though blood glucose levels remained high. This is the first study to show that selective inhibition of PI3K can attenuate the development of diabetes-induced abnormal vascular reactivity in the isolated carotid arteries of diabetic rats. Copyright © 2005 John Wiley & Sons, Ltd. [source] 4411: Immunohistochemical methods to evaluate vitreoretinal scaringACTA OPHTHALMOLOGICA, Issue 2010ML BOCHATON-PIALLAT Purpose Formation of scarlike epiretinal membranes (ERMs) constitutes potentially the end stage of evolution of proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR) and idiopathic vitreoretinopathy. Among various cellular populations, ERMs contain cells with contractile features typical of myofibroblasts. Myofibroblasts have been described in granulation tissue during wound healing and in practically all fibrocontractive diseases, in which they participate in the generation of isometric tension and in the synthesis of extracellular matrix components; these phenomena are in turn responsible for granulation tissue remodeling and retraction. The main marker of the myofibroblastic phenotype is the expression of alpha-SMA. The transforming growth factor-beta1 and the ED-A splice variant of cellular fibronectin, an extracellular matrix component, are key players of the complex process of myofibroblast differentiation. Methods Proteins were detected by means of immunohistochemical staining on paraffin sections from formol fixed tissues and double immunofluorescence staining on whole tissues. Samples were observed by using classical light and confocal microscopes. Results The presence of alpha-SM actin-positive myofibroblasts was associated with the expression of TGF-beta1, TGF-beta receptor II, and ED-A FN in all types of ERMs studied. Conclusion The results furnish new data on the mechanism of alpha-SM actin stimulation in fibroblasts in a human pathologic setting. [source] Role of Ca2+ mobilization and Ca2+ sensitization in 8-iso-PGF2, -induced contraction in airway smooth muscleCLINICAL & EXPERIMENTAL ALLERGY, Issue 2 2009A. Shiraki Summary Background Isoprostanes are prostaglandin (PG)-like compounds synthesized by oxidative stress, not by cyclooxygenase, and increase in bronchoalveolar lavage fluid of patients with asthma. The airway inflammation implicated in this disease may be amplified by oxidants. Although isoprostanes are useful biomarkers for oxidative stress, the action of these agents on airways has not been fully elucidated. Objective This study was designed to determine the intracellular mechanisms underlying the effects of oxidative stress on airway smooth muscle, focused on Ca2+ signalling pathways involved in the effect of 8-iso-PGF2,. Methods Using simultaneous recording of isometric tension and F340/F380 (an indicator of intracellular concentrations of Ca2+, [Ca2+]i), we examined the correlation between tension and [Ca2+]i in response to 8-iso-PGF2, in the fura-2 loaded tracheal smooth muscle. Results Augmented tension and F340/F380 by 8-iso-PGF2, were attenuated by ICI-192605, an antagonist of thromboxane A2 receptors (TP receptors). Moreover, D609, an antagonist of phosphatidylcholine-specific phospholipase C, markedly reduced both the tension and F340/F380 induced by 8-iso-PGF2,, whereas U73122, an antagonist of phosphatidylinositol-specific phospholipase C, modestly inhibited them by 8-iso-PGF2,. SKF96365, a non-selective antagonist of Ca2+ channels, markedly reduced both tension and F340/F380 by 8-iso-PGF2,. However, diltiazem and verapamil, voltage-dependent Ca2+ channel inhibitors, modestly attenuated tension although their reduction of F340/F380 was not different from that by SKF96365. Y-27632, an inhibitor of Rho-kinase, significantly attenuated contraction induced by 8-iso-PGF2, without reducing F340/F380, whereas GF109203X and Go6983, protein kinase C inhibitors, did not markedly antagonize them although reducing F340/F380 with a potency similar to Y-27632. Conclusion 8-iso-PGF2, causes airway smooth muscle contraction via activation of TP receptors. Ca2+ mobilization by SKF96365- and D609-sensitive Ca2+ influx and Ca2+ sensitization by Rho-kinase contribute to the intracellular mechanisms underlying the action of 8-iso-PGF2,. Rho-kinase may be a therapeutic target for the physiologic abnormalities induced by oxidative stress in airways. [source] Roles of P2X receptors and Ca2+ sensitization in extracellular adenosine triphosphate-induced hyperresponsiveness in airway smooth muscleCLINICAL & EXPERIMENTAL ALLERGY, Issue 6 2007T. Oguma Summary Background The release of adenosine triphosphate (ATP) from the airway epithelial cells during the inflammatory process is considered to play an important role in the pathophysiology of asthma and chronic obstructive pulmonary disease. Objective This study was designed to determine whether extracellular ATP is involved in the bronchial hyperresponsiveness as an interaction between epithelium and smooth muscle in the airways. Methods We examined the contractile response to methacholine (MCh) before and after exposure to low concentrations (10 ,m) of ATP in isolated, epithelium-denuded guinea-pig tracheal smooth muscle by measuring isometric tension. Intracellular Ca2+ concentrations ([Ca2+]i) were assessed by fluorescent intensities of fura-2. Results MCh-induced contractile force was increased with no change in [Ca2+]i after exposure to 10 ,m ATP for 15 min. The ability of ATP to enhance the MCh-induced contraction was markedly attenuated by suramin, a non-selective P2 receptor inhibitor. Pre-incubation with ATP,S, a non-hydrolysable analogue of ATP and ,,,-meATP, a P2X agonist, also enhanced the MCh-induced contraction. In contrast, uracil triphosphate, a P2Y agonist, did not affect the MCh-induced contraction. Y-27632, a Rho-kinase inhibitor, suppressed the ability of ATP to enhance the MCh-induced contraction. Moreover, PP1 and PP2, Src tyrosin kinase inhibitors, suppressed the enhancement of MCh-induced contraction by ATP. Conclusion Pre-treatment with ATP induces hyperresponsiveness to MCh mediated by Ca2+ sensitization via the P2X receptor in airway smooth muscle. The present findings suggest the possible involvement of both the Rho-kinase and Src pathways in the intracellular mechanism of this phenomenon. [source] Propofol differently alters vascular reactivity in normotensive and hypertensive ratsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2002Emmanuel Samain Summary 1.,The effect of propofol on arterial tone in hypertension is poorly understood. We examined the effect of increasing concentrations of propofol (5.6 × 10,8 to 2.8 × 10,3 mol/L) on isometric tension developed by noradrenaline (10,7 mol/L)-contracted aortic rings from 12-week-old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). 2.,In both WKY rats and SHR, propofol induced a dose-dependent inhibition of contraction induced by noradrenaline, but the amplitude of relaxation was larger in the SHR than in WKY rats. 3.,The effects of propofol was endothelium independent in WKY rats, whereas in SHR relaxation induced by propofol was greater in endothelium-intact than in endothelium-denuded rings. 4.,In conclusion, we found significant differences in the effect of propofol in hypertensive rats, which may be related to differences in structural and functional properties of the arterial wall observed in hypertension. [source] | |||||||||||||||||||||||||