Effect of Ileo-Jejunal transposition on ileal longitudinal smooth muscle contractility in vitro in rats

The aim of the present paper was to study the effects of ileo-jejunal transposition (IJT) on ileal contractile activity in vitro in rats. Male Sprague-Dawley rats were divided into three groups: control, IJT, and sham. In rats with IJT, the distal ileum was interposed isoperistaltically into the proximal jejunum. The jejunoileum was transected and anastomosed at three sites in the sham group. Rats were sacrificed 17–20 weeks postoperatively and the ileal segment was removed. Isometric contractile activity of the isolated ileal longitudinal muscle was measured in tissue chambers. Spontaneous contractile activity was decreased in the IJT group (0.16 ± 0.03 g/min per mg tissue) as compared with the control group (0.25 ± 0.02 g/min per mg tissue, p < 0.05). The motor response to cholinergic agonist bethanechol in the IJT group was greater than in the control group above 10^-6 M dosage. The dose-response curves to adrenergic agonist norepinephrine did not differ between groups. A nitric oxide synthase inhibitor reversed electrical field stimulation-induced inhibition of spontaneous activity in all groups. These results indicate that the response to bethanechol in the IJT group was enhanced in rat ileal longitudinal smooth muscle and this may be an adaptive response to compensate for decreased spontaneous contractile activity.     

Comparison of the effects of salbutamol and adrenaline on airway smooth muscle contractility in vitro and on bronchial reactivity in vivo.

BACKGROUND--The effect of adrenergic agonists in asthma depends on their net effect on microvascular leakage, mucosal oedema, vascular clearance of spasmogens, inhibition of cholinergic neurotransmission, and airway smooth muscle contractility. It has been postulated that adrenaline, by virtue of its alpha effects on the vasculature and cholinergic neurotransmission, may have additional useful properties in asthma compared with selective beta agonists such as salbutamol. METHODS--The airway effects of adrenaline (a non-selective adrenoreceptor agonist) were compared with the selective beta 2 agonist salbutamol. Their airway smooth muscle relaxant potencies and effect on histamine contraction in human bronchi in vitro were compared with their effects on airway calibre and histamine reactivity in asthmatic subjects in vivo. For the in vitro studies changes in tension were measured in response to these agents in thoracotomy specimens of human airways. In vivo the effects of adrenaline and salbutamol on airway calibre and histamine reactivity were measured in eight subjects with mild to moderate asthma in a randomised crossover study. RESULTS--Salbutamol and adrenaline had approximately equivalent airway smooth muscle relaxant potencies in vitro and bronchodilator potency in vivo. However, their effects on histamine induced contraction in vitro were significantly different from their effects on histamine reactivity in vivo. Salbutamol was less potent in vitro producing a mean (SE) 2.4 (0.15) doubling dose increase in the histamine EC20 and adrenaline a 5.2 (0.18) doubling dose increase (mean difference between salbutamol and adrenaline 2.8 doubling doses; 95% CI 1.1 to 4.5). Salbutamol had no effect on the maximal response to histamine whereas adrenaline reduced it by 54%. In contrast, salbutamol was more potent in vivo producing a mean (SE) increase in PD20 histamine of 1.84 (0.5) doubling doses whereas adrenaline was without effect increasing PD20 by only 0.06 (0.47) doubling doses (mean difference between adrenaline and salbutamol 1.78, 95% CI 0.26 to 3.29 doubling doses). CONCLUSIONS--These findings suggest that the alpha adrenergic airway effects of non-selective adrenoreceptor agonists such as adrenaline offer no additional protection against histamine-induced broncho-constriction in vivo than beta 2 selective drugs such as salbutamol, despite adrenaline providing greater protection against histamine-induced contraction in vitro. The differences between the effects of these agents in vitro and in vivo may be related to their opposing vascular effects in vivo.     

Effect of peritonitis on gallbladder smooth muscle contractility in guinea pigs

BACKGROUND: The mechanisms involved in the impaired gallbladder contractile response in peritonitis are unknown. The aim of this study was to determine the effect of peritonitis on the contraction and relaxation responses to different agonists in gallbladder smooth muscle in guinea pig. MATERIALS AND METHODS: Peritonitis was induced by cecal ligation and puncture (CLP) in 10 guinea pigs. Another group of 10 guinea pigs underwent a sham operation and acted as controls. Twenty-four hours after the operation, the guinea pigs were killed, and gallbladder strips were placed in organ bath. The contraction responses to KCl, carbachol, and histamine, and relaxation responses to cyclooxygenase inhibitors (indomethacin, nimesulide, and DFU) on KCl-induced contractions were recorded. RESULTS: There was no significant difference between the contractile responsiveness to KCl, but maximum contractile responses (E(max)) to carbachol and histamine were significantly reduced. Indomethacin, nimesulide, and DFU concentration dependently inhibited on KCl-induced contractions of gallbladder smooth muscle. E(max) values of indomethacin, nimesulide, and DFU were significantly reduced in the peritonitis group compared with controls (P < 0.05). The inhibitor effects of nimesulide and DFU were considerably similar, but inhibitor effect of indomethacin was significantly less than that measured for nimesulide and DFU in both control and peritonitis groups (P < 0.05). CONCLUSIONS: The contraction responses to carbachol and histamine and relaxation responses to COX inhibitors on gallbladder smooth muscle are significantly decreased by peritonitis. Although the mechanism of the decrease in contraction and relaxation responses in CLP-induced peritonitis is completely unknown, we speculate that impaired smooth muscle responses may be related to an alteration in the regulation of receptor/postreceptor excitation-response coupling and/or through changes on Ca(2+) influx.     

Effects of sodium metabisulphite on guinea pig contractile airway smooth muscle responses in vitro.

BACKGROUND--Sodium metabisulphite (MBS) is known to induce bronchoconstriction in asthmatic patients. The effects of MBS on guinea pig airway smooth muscle and on neurally mediated contraction in vitro have been examined. METHODS--Tracheal and bronchial airway segments were placed in oxygenated buffer solution and electrical field stimulation was performed in the presence of indomethacin (10(-5) M) and propranolol (10(-6) M) for the measurement of isometric tension. Atropine (10(-6) M) was added to bronchial tissues. RESULTS--Concentrations of MBS up to 10(-3) M had no direct effect on airway smooth muscle contraction and did not alter either tracheal smooth muscle contraction induced by electrical field stimulation at all frequencies or acetylcholine-induced tracheal smooth muscle contraction. There was a similar response in the absence of epithelium, except for potentiation of the response induced by electrical field stimulation at 0.5 Hz (24 (10)% increase). However, MBS (10(-5), 10(-6) and 10(-7) M) augmented neurally-mediated non-adrenergic non-cholinergic contractile responses in the bronchi (13.3 (3.2)%, 23.8 (9.6)%, and 6.4 (1.6)%, respectively). MBS had no effect on the contractile response induced by substance P, but at higher concentrations (10(-3) M and 10(-4) M) it caused a time-dependent attenuation of responses induced by either electrical field stimulation or exogenously applied acetylcholine or substance P. CONCLUSIONS--MBS had no direct contractile responses but enhanced bronchoconstriction induced by activation of non-cholinergic neural pathways in the bronchus, probably through increased release of neuropeptides. At high concentrations MBS inhibited contractile responses initiated by receptor or neural stimulation.     

Effect of different bronchodilators on airway smooth muscle responsiveness to contractile agents.

"Functional antagonism" is often used to describe the general relaxant effect of beta 2 agonists and xanthines and their ability to protect the airways against bronchoconstrictor stimuli. This study in guinea pig isolated trachea addresses the question of whether the capacity of these drugs to protect against constrictor stimuli is related to smooth muscle relaxation. Three antimuscarinic drugs were also examined to determine whether antagonism of mediators other than muscarinic agonists might contribute to bronchodilatation by these antimuscarinic drugs. Terbutaline (1.1 x 10(-7), 2.2 x 10(-7) M), theophylline (2.2 x 10(-4), 4.4 x 10(-4) M), and enprofylline (5.2 x 10(-5), 1.0 x 10(-4) M) relaxed the tracheal tension that remained after indomethacin treatment. They did not, however, alter the carbachol concentration-response curve significantly. In addition, neither theophylline (2.2 x 10(-4) M) nor terbutaline (1.1 x 10(-7) M) altered histamine induced contraction. Atropine sulphate, glycopyrrolate, and ipratropium bromide had EC50 values of 10(-9) - 10(-8) M for relaxation of carbachol induced contractions, whereas concentrations of 10(-6) - 10(-3) M or greater were required to relax contractions induced by allergen and nine other non-muscarinic mediators. It is suggested that bronchodilatation by antimuscarinic drugs in vivo is due to inhibition of acetylcholine induced bronchoconstriction alone and that beta 2 agonists and xanthines have poor ability to protect airway smooth muscle against constrictor stimuli. Hence mechanisms other than bronchodilatation and "functional antagonism" should be considered to explain the protection against constrictor stimuli in asthma seen with beta 2 agonists and xanthines.     

Halothane increases smooth muscle protein phosphatase in airway smooth muscle

BACKGROUND: Halothane relaxes airway smooth muscle, in part, by decreasing the force produced for a given intracellular [Ca(2+)] (i.e., Ca(2+) sensitivity) during muscarinic stimulation, an effect produced by a decrease in regulatory myosin light-chain (rMLC) phosphorylation. The authors tested the hypothesis that halothane reduces rMLC phosphorylation during muscarinic stimulation at constant intracellular [Ca(2+)] by increasing smooth muscle protein phosphatase (SMPP) activity, without changing myosin light-chain kinase (MLCK) activity. METHODS: Enzyme activities were assayed in beta-escin permeabilized strips of canine tracheal smooth muscle. Under conditions of constant intracellular [Ca(2+)], the rate of rMLC phosphorylation was measured by Western blotting during inhibition of SMPP with microcystin-LR (to assay MLCK activity) or during inhibition of MLCK by wortmannin and adenosine triphosphate depletion (to assay SMPP activity). The effect of halothane (0.8 mm) on enzyme activities and isometric force during stimulation with 0.6 microm Ca(2+) and 10 microm acetylcholine was determined. RESULTS: Halothane produced a 14 +/- 8% (mean +/- SD) decrease in isometric force by significantly reducing rMLC phosphorylation (from 32 +/- 9% to 28 +/- 9%). Halothane had no significant effect on any parameter of a monoexponential relation fit to the data for the MLCK activity assay. In contrast, halothane significantly decreased the half-time for rMLC dephosphorylation in the SMPP activity assay (from 0.74 +/- 0.28 min to 0.44 +/- 0.10 min), indicating that it increased SMPP activity. CONCLUSIONS: Halothane decreases Ca(2+) sensitivity and rMLC phosphorylation in airway smooth muscle during muscarinic receptor stimulation by increasing SMPP activity, without affecting MLCK, probably by disrupting receptor G-protein signaling pathways that inhibit SMPP.     

Different inhibitory effects of sevoflurane on hyperreactive airway smooth muscle contractility in ovalbumin-sensitized and chronic cigarette-smoking guinea pig models

BACKGROUND: The authors hypothesized that sevoflurane had different inhibitory effects on hyperreactive airway smooth muscle contractility in different types of hyperreactive airway models. METHODS: The effects of sevoflurane on hyperreactive airways in ovalbumin-sensitized and chronic cigarette-smoking guinea pig models were investigated by measuring (1) total lung resistance, (2) smooth muscle tension and intracellular concentration of free Ca, (3) voltage-dependent Ca channel activity, and (4) cyclic adenosine monophosphate levels. RESULTS: Ovalbumin and muscarinic airway hyperreactivity was seen in ovalbumin-sensitized animals. Enlarged alveolar ducts/alveoli and lesser muscarinic hyperreactivity were observed in chronic cigarette-smoke animals. Although sevoflurane inhibited the acetylcholine-induced increase in total lung resistance in the control and ovalbumin-sensitized models, the anesthetic had a smaller effect in the chronic cigarette-smoking model. Similarly, in the chronic cigarette-smoking model, sevoflurane had a smaller inhibitory effect on carbachol-induced muscle contraction and increase in intracellular concentration of free Ca. Sevoflurane also had a smaller inhibitory effect on voltage-dependent Ca channel activity in the chronic cigarette-smoking group than in the other two groups. The sevoflurane-induced increase in cyclic adenosine monophosphate that was seen in the control and ovalbumin-sensitized groups was significantly suppressed in the chronic cigarette-smoking group. CONCLUSIONS: Although sevoflurane potently inhibited airway contractility in control and ovalbumin-sensitized models, the anesthetic had a smaller effect in a chronic cigarette-smoking model. The different inhibitory effects of sevoflurane on airway contractility depend, at least in part, on different effects on voltage-dependent Ca channel activity and cyclic adenosine monophosphate level.     

Effects of acid-base changes on human ureteric smooth muscle contractility

Wide fluctuations of both urinary pH and the partial pressure of CO2 (PCO2) occur in normal physiological circumstances and in a variety of pathological conditions. However, the effect of extracellular pH on the contractility of human ureteric muscle has not been clearly defined. This study has established, using a microsuperfusion technique, that an increased superfusate PCO2 increases the magnitude of the phasic contraction to electrical field stimulation. A similar extracellular acidosis induced by alteration of the [HCO3-], at constant [Na+] and free [Ca2+], was without significant effect. Furthermore, when both superfusate PCO2 and [HCO3-] were simultaneously increased at constant pH the contractile response was similar to that when PCO2 alone was raised. These observations suggest that the changes of tension were mediated by intracellular pH changes, providing it is assumed that the ureteric smooth muscle cell membrane is permeable to CO2 but impermeable to H+ and HCO3-. The occurrence of an increase of force in the presence of an acidosis is a highly significant and unusual finding, since it has been assumed that the classical association between acidosis and negative inotropy, seen in cardiac muscle, was also applicable to smooth muscle.     

Effects of primary alcohols on airway smooth muscle

BACKGROUND: The investigation examined whether primary alcohols could be used as tools to explore the mechanism of anesthetic actions in airway smooth muscle (ASM). The hypothesis was that, like volatile anesthetics, the primary alcohols relax intact ASM by decreasing intracellular Ca2+ concentration ([Ca2+]i) and by inhibiting agonist-induced increases in the force developed for a given [Ca2+]i (Ca2+ sensitivity). METHOD: The effects of butanol, hexanol, and octanol on isometric force in canine tracheal smooth muscle were examined. The effects of hexanol on [Ca2+]i (measured with fura-2) and the relationship between force and [Ca2+]i were studied during membrane depolarization provided by KCl and during muscarinic stimulation provided by acetylcholine. RESULTS: The primary alcohols relaxed ASM contracted by KCl or acetylcholine in a concentration-dependent manner, with potency increasing as chain length increased. The alcohols could completely relax the strips, even during maximal stimulation with 10 microM acetylcholine (median effective concentrations of 28 +/- 12, 1.3 +/- 0.4, and 0.14 +/- 0.05 mM [mean +/- SD] for butanol, hexanol, and octanol, respectively). Hexanol decreased both [Ca2+]i and force in a concentration-dependent manner. Hexanol decreased Ca2+ sensitivity during muscarinic stimulation but had no effect on the force-[Ca2+]i relationship in its absence. CONCLUSIONS: Primary alcohols produce reversible, complete relaxation of ASM, with potency increasing as chain length increases, by decreasing [Ca2+]i and inhibiting increases in Ca2+ sensitivity produced by muscarinic receptor stimulation. These actions mimic those of volatile anesthetics on ASM, a circumstance suggesting that the primary alcohols may be useful tools for further exploring mechanisms of anesthetic effects on ASM.     

Effect of glycine on recovery of bladder smooth muscle contractility after acute urinary retention in rats

OBJECTIVE: To investigate the effects of glycine on the recovery of bladder smooth muscle contractility after acute urinary retention. MATERIALS AND METHODS: Bladder overdistension was induced in Sprague-Dawley rats by an infusion of saline (twice the threshold volume), maintained for 2 h. From 15 min before emptying of the bladder until 2 h after, saline or glycine solution was infused i.v. At 30 min, 2 h and 1 week after bladder emptying, samples of bladder tissue were taken for muscle strip study, malondialdehyde (MDA) assay, ATP assay, Western blotting for apoptosis-related molecules (Bcl-2, Bax, Caspase-3), and histological analysis including terminal deoxynucleotidyl transferase-mediated nick-end labelling staining. The results were compared among normal control, saline-treated and glycine-treated rats. RESULTS: In the glycine-treated group, muscle strip contractile responses induced by electrical-field stimulation and carbachol were both significantly greater at 1 week after bladder emptying than in the saline-treated group. The results of the ATP assay appeared to correspond with those of the muscle strip study. The saline-treated group had significantly higher MDA levels at 30 min after bladder emptying than the glycine-treated group. At 2 h after bladder emptying, there was significantly more apoptosis and greater leukocyte infiltration in the saline-treated group than in the glycine-treated group. While pro-apoptotic Bax and caspase-3 were down-regulated, Bcl-2 was up-regulated in the glycine-treated group. CONCLUSION: Glycine infusions might improve the contractile responses of bladder smooth muscle after acute urinary retention by reducing oxidative damage and apoptosis.     

Gastric smooth muscle contractility changes in the esophageal atresia rat model: an in vitro study

Purpose: The aim of the study was to investigate the gastric smooth muscle reactivity in the Adriamycin-induced esophageal atresia (EA) rat model.Methods: The fetuses were divided into 3 groups. The control group was exposed to saline. The second group was comprised of fetuses that were exposed to Adriamycin but did not have EA (Adriamycin-no-EA group). The third group was comprised of fetuses that were exposed to Adriamycin and had EA (Adriamycin-EA group). Gastric fundus strips were studied in vitro for their contractile response to receptor activation in the 3 groups.Results: Contractile responses of gastric smooth muscle to carbachol and KCl were increased in the Adriamycin-EA group compared with the Adriamycin-no-EA group. Also serotonin-induced contractile response in the Adriamycin-EA group decreased compared with the Adriamycin-no-EA group. Relaxation of gastric smooth muscle strips to isoproterenol was comparably unaffected in the Adriamycin-EA and Adriamycin-no-EA groups. Likewise, no change in the response to agonist studies was observed between the control and Adriamycin-no-EA groups. The relaxant response to papaverine was not different in the 3 groups.Conclusions: This study found changes of receptor-dependent and receptor-independent contraction of the gastric fundus smooth muscle in the fetuses with EA. Therefore, impaired contractile responses may be, at least in part, a contributing factor in the abnormal gastric motility seen in EA.     

Effects of changes in pH on the contractility of vascular smooth muscle

Hydrogen ion concentration (H+) is an important regulator of many cellular functions including contractility of the vascular smooth muscle cells. In many physiological and pathological states, changes in pH may have profound effects on the contractility of blood vessels and thus on the peripheral vascular resistance and blood pressure. Therefore, it is necessary to understand the likely outcome of the situations in the conditions, where pH changes are frequent. In this review, the mechanisms involved in the contractile responses of vascular tissues to pH changes are discussed.     

Effects of ovariectomy and steroid hormones on vaginal smooth muscle contractility

The role of steroid hormones in regulating vaginal smooth muscle contractility was investigated. Rabbits were kept intact or ovariectomized. After 2 weeks, animals were continuously infused with vehicle or supraphysiological levels of testosterone (100 microg/day), or estradiol (200 microg/day), for an additional 2 weeks. The distal vaginal tissue was used to assess contractility in organ baths and changes in tissue structure were assessed by histology. Ovariectomized animals infused with vehicle exhibited significant atrophy of the muscularis and decreased epithelial height, resulting in thinning of the vaginal wall. Estradiol infusion increased epithelial height, comparable to that of intact animals, but only partially restored the muscularis layer. In contrast, testosterone infusion completely restored the muscularis layer, but only partially restored the epithelial height. In vaginal tissue strips contracted with norepinephrine and treated with bretylium, electrical field stimulation (EFS) caused frequency-dependent relaxation that was slightly attenuated with vehicle, significantly inhibited with estradiol and significantly enhanced with testosterone. VIP-induced relaxation was slightly attenuated in tissues from vehicle and estradiol-infused groups, but was enhanced in tissues from testosterone-infused animals. Contraction elicited by EFS or exogenous norepinephrine was not significantly altered with ovariectomy or steroid hormone infusion when data were normalized to potassium contraction. However, the tissue from testosterone-infused animals developed significantly greater contractile force to norepinephrine. These observations suggest that steroid hormones may be important regulators of vaginal tissue structure and contractility.     

Interleukin-17 stimulates release of interleukin-8 by human airway smooth muscle cells in vitro: a potential role for interleukin-17 and airway smooth muscle cells in bronchiolitis obliterans syndrome.

Bronchiolitis obliterans syndrome is the major constraint on the long-term survival after lung transplantation. Both neutrophils and interleukin (IL)-8, a potent neutrophil attractant, have been shown to play an important role in the pathophysiology of obliterative bronchiolitis. We investigated the potential role of human airway smooth muscle cells in obliterative bronchiolitis by studying their release of IL-8 after stimulation with IL-17, a novel T-cell-derived chemokine capable of attracting and activating neutrophils. We demonstrated a significant increase in IL-8 release, reaching a concentration of 86.6 ng/ml (SEM 1.9 ng/ml) with 100 ng/ml IL-17 (p < 0.01, n = 4), as compared with non-stimulated cells. This IL-17-mediated IL-8 release could not be inhibited by dexamethasone. We conclude that human airway smooth muscle cells may play an important pro-inflammatory role in neutrophilic inflammatory diseases such as chronic rejection after lung transplantation; furthermore, IL-17 may be the link between lymphocytes and neutrophils.     

利多卡因对气管平滑肌舒张作用的研究

利多卡因是临床上常用的局部麻醉药和抗室性心律失常药物;除此之外,利多卡因还具有较强的扩张气道、抑制气道炎症、降低气道高反应性的作用。此方面的研究最早可追溯到上世纪60年代,利多卡因在围术期预防和处理支气管痉挛中所占的地位已得到充分肯定,现将近10余年来利多卡因对气道平滑肌影响的主要研究成果综述如下。     

咪唑安定对气管平滑肌舒张作用的研究

咪唑安定对气管平滑肌有直接舒张作用,作用机制主要和抑制电压依赖性钙通道,降低细胞内钙离子浓度有关;对PKC信号转导系统也有一定的抑制作用;咪唑安定雾化吸入有引起支气管痉挛的可能。