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Isolated Smooth Muscle Cells (isolated + smooth_muscle_cell)
Selected AbstractsEffect of otilonium bromide on contractile patterns in the human sigmoid colonNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2010D. Gallego Abstract Background, The mechanism of action of the spasmolytic compound otilonium bromide (OB) on human colonic motility is not understood. The aim of our study was to characterize the pharmacological effects of OB on contractile patterns in the human sigmoid colon. Methods, Circular sigmoid strips were studied in organ baths. Isolated smooth muscle cells from human sigmoid colon were examined using the calcium imaging technique. Key Results, Otilonium bromide inhibited by 85% spontaneous non-neural rhythmic phasic contractions (RPCs), (IC50 = 49.9 nmol L,1) and stretch-induced tone (IC50 = 10.7 nmol L,1) with maximum effects at micromolar range. OB also inhibited by 50% both on- (IC50 = 38.0 nmol L,1) and off- contractions induced by electrical stimulation of excitatory motor neurons. In contrast, the inhibitory latency period prior to off -contractions was unaffected by OB. OB inhibited acetylcholine-, substance P-, and neurokinin A-induced contractions. The L-type Ca2+ channel agonist BayK8644 reversed the effects of OB on RPCs, on- and off -contractions. Hexamethonium, atropine, the NK2 antagonist, or depletion of intracellular Ca2+ stores by thapsigargin did not prevent the inhibitory effect of OB on RPCs and electrical contractions. KCl-induced calcium transients in isolated smooth muscle cells were also inhibited by OB (IC50 = 0.2 ,mol L,1). Conclusions & Inferences, Otilonium bromide strongly inhibited the main patterns of human sigmoid motility in vitro by blocking calcium influx through L-type calcium channels on smooth muscle cells. This pharmacological profile may mediate the clinically observed effects of the drug in patients with irritable bowel syndrome. [source] Oxytocin receptor expressed on the smooth muscle mediates the excitatory effect of oxytocin on gastric motility in ratsNEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2009J. Qin Abstract, The aim of this study was to localize oxytocin receptor (OTR) in the stomach and to investigate the effect of OT on gastric motility in rats. Western blot and immunohistochemistry methods were used to localize OTR in stomach. The motility of stomach was recorded in vivo (recording of the intragastric pressure), in vitro (recording of the contraction of muscle strips) and on isolated smooth muscle cells. OTR was expressed on cells of both circular and longitudinal muscle of stomach. Systemic administration of OT induced an early transient decrease and a subsequent increase on intragastric pressure. Devazepide (1 mg kg,1, i.v.), a cholecystokinin-1 (CCK1) receptor antagonist, completely abolished the transient response but did not influence the subsequent one. OT (10,9,10,6 mol L,1) dose-dependently increased the contraction of the muscle strips of gastric body, antrum, and pyloric sphincter, and decreased the average cell length of isolated smooth muscle cells. Tetrodotoxin and atropine did not influence the effect of OT on muscle strips. Pretreatment with atosiban, an OTR antagonist, inhibited the spontaneous contraction of muscle strips and abolished the excitatory effect of OT on the muscle strips and the isolated cells. These results suggest that the OTR is expressed on the smooth muscle of the stomach and mediates excitatory effect of OT on gastric motility. [source] Spontaneous Ca2+ Waves in Rabbit Corpus Cavernosum: Modulation by Nitric Oxide and cGMPTHE JOURNAL OF SEXUAL MEDICINE, Issue 4 2009Gerard P. Sergeant PhD ABSTRACT Introduction., Detumescent tone and subsequent relaxation by nitric oxide (NO) are essential processes that determine the erectile state of the penis. Despite this, the mechanisms involved are incompletely understood. It is often assumed that the tone is associated with a sustained high cytosolic Ca2+ level in the corpus cavernosum smooth muscle cells, however, an alternative possibility is that oscillatory Ca2+ signals regulate tone, and erection occurs as a result of inhibition of Ca2+ oscillations by NO. Aims., The aim of this study is to determine if smooth muscle cells displayed spontaneous Ca2+ oscillations and, if so, whether these were regulated by NO. Methods., Male New Zealand white rabbits were euthanized and smooth muscle cells were isolated by enzymatic dispersal for confocal imaging of intracellular Ca2+ (using fluo-4AM) and patch clamp recording of spontaneous membrane currents. Thin tissue slices were also loaded with fluo-4AM for live imaging of Ca2+. Main Outcome Measure., Cytosolic Ca2+ was measured in isolated smooth muscle cells and tissue slices. Results., Isolated rabbit corpus cavernosum smooth muscle cells developed spontaneous Ca2+ waves that spread at a mean velocity of 65 µm/s. Dual voltage clamp/confocal recordings revealed that each of the Ca2+ waves was associated with an inward current typical of the Ca2+ -activated Cl - currents developed by these cells. The waves depended on an intact sarcoplasmic reticulum Ca2+ store, as they were blocked by cyclopiazonic acid (Calbiochem, San Diego, CA, USA) and agents that interfere with ryanodine receptors and IP3 -mediated Ca2+ release. The waves were also inhibited by an NO donor (diethylamine NO; Tocris Bioscience, Bristol, Avon, UK), 3-(5-hydroxymethyl-2-furyl)-1-benzyl indazole (YC-1) (Alexis Biochemicals, Bingham, Notts, UK), 8-bromo-cyclic guanosine mono-phosphate (Tocris), and sildenafil (Viagra, Pfizer, Sandwich, Kent, UK). Regular Ca2+ oscillations were also observed in whole tissue slices where they were clearly seen to precede contraction. This activity was also markedly inhibited by sildenafil, suggesting that it was under NO regulation. Conclusions., These results provide a new basis for understanding detumescent tone in the corpus cavernosum and its inhibition by NO. Sergeant GP, Craven M, Hollywood MA, McHale NG, and Thornbury KD. Spontaneous Ca2+ waves in rabbit corpus cavernosum: Modulation by nitric oxide and cGMP. J Sex Med **;**:**,**. [source] Electrophysiological effects of endothelin-1 and their relationship to contraction in rat renal arterial smooth muscleBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2000Luisa C Betts The electophysiological effects of endothelin-1 (ET-1) and their relationship to contraction remain unclear in the renal circulation. Using endotheliumdenuded arteries from the main branch of the renal artery proximal to the kidney of the rat, we have examined its effects on tension and conducted parallel patch-clamp measurements using freshly isolated smooth muscle cells from this tissue. Pharmacological experiments revealed that ET-1 produced constriction of renal arteries dependent on the influx of extracellular Ca2+, mediated solely through ETA receptor stimulation. Current-clamp experiments revealed that renal arterial myocytes had a resting membrane potential of ,32 mV, with the majority of cells exhibiting spontaneous transient hyperpolarizations (STHPs). Application of ET-1 produced depolarization and in those cells exhibiting STHPs, either caused their inhibition or made them occur regularly. Under voltage-clamp conditions cells were observed to exhibit spontaneous transient outward currents (STOCs) inhibited by iberiotoxin. Application of voltage-ramps revealed an outward current activated at ,,30 mV, sensitive to both 4-AP and TEA. Taken together these results suggest that renal arterial myocytes possess both delayed rectifying K+ (KV) and Ca2+ -activated K+ (BKCa) channels. Under voltage-clamp, ET-1 attenuated the outward current and reduced the magnitude and incidence of STOCs: effects mediated solely as a consequence of ETA receptor stimulation. Thus, in conclusion, activation of ETA receptors by ET-1 causes inhibition of KV and BKCa channel activity, which could promote and/or maintain membrane depolarization. This effect is likely to favour L-type Ca2+ channel activity providing an influx pathway for extracellular Ca2+ essential for contraction. British Journal of Pharmacology (2000) 130, 787,796; doi:10.1038/sj.bjp.0703377 [source] | ||||||||||