Methods: Freshly isolated rat ventricular myocytes were obtained from adult rat hearts. Myocyte shortening, [Ca2+]i, nitric oxide production, intracellular pH, and action potentials were monitored in cardiomyocytes exposed to droperidol. Langendorff perfused hearts were used to assess overall cardiac function.
Results: Droperidol (0.03-1 [mu]m) caused concentration-dependent decreases in peak [Ca2+]i and shortening. Droperidol inhibited 35 mm KCl-induced increase in [Ca2+]i, with little direct effect on sarcoplasmic reticulum Ca2+ stores. Droperidol had no effect on action potential duration but caused a rightward shift in the concentration-response curve to extracellular Ca2+ for shortening, with no concomitant effect on peak [Ca2+]i. Droperidol decreased pHi and increased nitric oxide production. Droperidol exerted a negative inotropic effect in Langendorff perfused hearts. 相似文献
Methods: Single rat ventricular myocytes loaded with fura-2 were electrically stimulated at 1 Hz, and the Ca2+ transients and contractions were recorded optically. Cells were exposed to each anesthetic for 1 min. Changes in myofilament Ca2+ sensitivity were assessed by comparing the changes in the Ca2+ transient and contraction during exposure to anesthetic and low Ca2+. SR Ca2+ content was assessed by exposure to 20 mm caffeine.
Results: Isoflurane and halothane caused a depression of myofilament Ca2+ sensitivity, unlike sevoflurane, which had no effect on myofilament Ca2+ sensitivity. All three anesthetics decreased the electrically stimulated Ca2+ transient. SR Ca2+ content was reduced by both isoflurane and halothane but was unchanged by sevoflurane. Fractional release was reduced by both isoflurane and sevoflurane, but was unchanged by halothane. 相似文献
Methods: Cytosolic [Ca2+] was measured by fluorescence at the left ventricular wall of guinea pig isolated hearts using indo-1 dye. Sarcoplasmic reticular Ca2+-cycling proteins, i.e., Ca2+ release channel (ryanodine receptor [RyR2]), sarcoplasmic reticular Ca2+-pump adenosine triphosphatase (SERCA2a), and phospholamban were measured by Western blots. Hearts were assigned to seven groups (n = 8 each): (1) time control; (2) ischemia; (3, 4) 10 [mu]m Na+-Ca2+ exchange inhibitor KB-R7943 (KBR) or 1 [mu]m SEA0400 (SEA), given during the first 10 min of reperfusion; (5) APC initiated by sevoflurane (2.2%, 0.41 +/- 0.03 mm) given for 15 min and washed out for 15 min before ischemia-reperfusion; (6, 7) APC plus KBR or SEA.
Results: The authors found that APC reduced the increase in systolic [Ca2+], whereas KBR and SEA both reduced the increase in diastolic [Ca2+] on reperfusion. Each intervention improved recovery of left ventricular function. Moreover, APC plus KBR or SEA afforded better functional recovery than APC, KBR, or SEA alone (P < 0.05). Ischemia-reperfusion-induced degradation of major sarcoplasmic reticular Ca2+-cycling proteins was attenuated by APC, but not by KBR or SEA. 相似文献
Methods: Freshly isolated adult rat ventricular myocytes were used for the study. Cardiac myofibrils were extracted for assessment of myofibrillar actomyosin adenosine triphosphatase (ATPase) activity. Myocyte shortening (video edge detection) and pHi (2',7'-bis-(2-carboxyethyl)-5(6')-carboxyfluorescein, 500/440 ratio) were monitored simultaneously in individual cells field-stimulated (0.3 Hz) and superfused with HEPES-buffered solution (pH 7.4, 30[degrees]C).
Results: Propofol (100 [mu]m) reduced the Ca2+ concentration required for activation of myofibrillar actomyosin ATPase from pCa 5.7 +/- 0.01 to 6.6 +/- 0.01. Increasing pHi (7.05 +/- 0.03 to 7.39 +/- 0.04) with NH4Cl increased myocyte shortening by 35 +/- 12%. Washout of NH4Cl decreased pHi to 6.82 +/- 0.03 and decreased myocyte shortening to 52 +/- 10% of control. Propofol caused a dose-dependent increase in pHi but reduced myocyte shortening. The propofol-induced increase in pHi was attenuated, whereas the decrease in myocyte shortening was enhanced after pretreatment with ethylisopropyl amiloride, a Na+-H+ exchange inhibitor, or bisindolylmaleimide I, a protein kinase C inhibitor. Propofol also attenuated the NH4Cl-induced intracellular acidosis, increased the rate of recovery from acidosis, and attenuated the associated decrease in myocyte shortening. Propofol caused a leftward shift in the extracellular Ca2+-shortening relation, and this effect was attenuated by ethylisopropyl amiloride. 相似文献
Methods: Saponin skinned muscle fibers from the extensor digitorum longus muscle of BALB/c mice were examined according to a standardized procedure described previously. For the assessment of effects on Ca2+ uptake and release from the SR, bupivacaine was added to the loading solution and the release solution, respectively. Force transients and force decays were monitored, and the position of the curve relating relative isometric force versus free [Ca2+] was evaluated in the presence or absence of bupivacaine.
Results: Bupivacaine induces Ca2+ release from the SR. In addition, the Ca2+ loading procedure is suppressed, resulting in smaller caffeine-induced force transients after loading in the presence of bupivacaine. The decay of caffeine-induced force transients is reduced by bupivacaine, and it also shifts [Ca2+]-force relation toward lower [Ca2+]. 相似文献
Methods: The authors studied the effects of bupivacaine and the similarly lipid-soluble local anesthetic, tetracaine, on the Ca2+ release channel-ryanodine receptor of sarcoplasmic reticulum in swine skeletal and cardiac muscle. [(3) H]Ryanodine binding was used to measure the activity of the Ca2+ release channel-ryanodine receptors in microsomes of both muscles.
Results: Bupivacaine enhanced (by two times at 5 mM) and inhibited (66% inhibition at 10 mM) [(3) H]ryanodine binding to skeletal muscle microsomes. In contrast, only inhibitory effects were observed with cardiac microsomes (about 3 mM for half-maximal inhibition). Tetracaine, which inhibits [(3) H]ryanodine binding to skeletal muscle microsomes, also inhibited [(3) H]ryanodine binding to cardiac muscle microsomes (half-maximal inhibition at 99 [micro sign]M). 相似文献
Methods: Hippocampal slices from 5-day-old, 1-month-old, and 19- to 23-month-old rats were deprived of oxygen and glucose for 5-30 min in media bubbled with 1% isoflurane. Cell death was assessed in the CA1, CA3, and dentate regions, and intracellular Ca2+ concentration was measured in CA1 neurons. N-methyl-d-aspartate receptor (NMDAR)-dependent Ca2+ influx was measured and the phosphorylation of NMDARs, and the survival proteins Akt and mitogen-activated protein kinase p42/44 were quantified.
Results: Twenty minutes of oxygen and glucose deprivation killed approximately 40-60% of neurons in CA3 and dentate in all age groups. Isoflurane, 1%, reduced death of CA1, CA3, and dentate neurons in slices from 5-day-old rats but not those from 23-month-old rats. In 5-day slices, isoflurane attenuated NMDAR-mediated Ca2+ influx, whereas in aging slices, Ca2+ influx was increased protein kinase C. In aging slices, isoflurane did not increase the phosphorylation of Akt and p42/44. 相似文献
Methods: Whole-cell patch-clamp recording techniques were used to evaluate the effects of the benzodiazepines diazepam (10-8 to 10-3 M) and midazolam (10-8 to 10-3 M) on inward Ca2+ and outward K (+) channel currents in dispersed canine tracheal smooth muscle cells. The effects of the antagonists flumazenil (10-5 M) and PK11195 (10-5 M) on these channels were also studied.
Results: Each benzodiazepine tested significantly inhibited Ca2+ currents in a dose-dependent manner, with 10-6 M diazepam and 10-5 M midazolam each causing approximately 50% depression of peak voltage-dependent Ca2+ currents. Both benzodiazepines promoted the inactivated state of the channel at more-negative potentials. The Ca2+ -activated and voltage-dependent K+ currents were inhibited by diazepam and midazolam (> 10-5 M and > 10-4 M, respectively). Flumazenil and PK11195 had no effect on these channel currents or on the inhibitory effects of the benzodiazepines. 相似文献
Methods: Rat ventricular muscle was used. First, the effect of bupivacaine was examined on tetanic contractions in isolated intact myocytes. Next, Triton X-100-treated ventricular trabeculae were used to investigate the effect of bupivacaine on the pCa (= -log [Ca2+])-tension relation as well as on maximal Ca2+-activated tension. Furthermore, to test whether bupivacaine inhibits the pathway downstream from Ca2+ binding to troponin C, tension was elicited in the skinned preparations by lowering the Mg-adenosine triphosphate (MgATP) concentration in the absence of Ca2+. The effect of bupivacaine on the pMgATP (= -log [MgATP])-tension relation was examined.
Results: In myocytes, 3 [mu]m bupivacaine significantly (P < 0.01) increased intracellular Ca2+ concentration required for 5% cell shortening from the resting cell length. In skinned preparations, bupivacaine shifted the pCa-tension relation to the lower pCa side; the midpoint of the pCa curve (pCa50) was significantly (P < 0.05) changed by 10 and 100 [mu]m bupivacaine. A highly correlated linear relation (R = 0.81;P < 0.0005) was present between pCa50 and maximal Ca2+-activated tension. Bupivacaine (10 and 100 [mu]m) significantly (P < 0.05) shifted the midpoint of the pMgATP-tension relation to the higher pMgATP side. 相似文献
Methods: IK, SK1, and chimera channels were expressed in Xenopus laevis oocytes. Currents of expressed channels were measured in the presence of 10 [mu]m Ca2+ by excised patch clamp analysis. Time constants of inhibition by halothane were compared between inside-out and outside-out patch configurations.
Results: Currents from chimera channels possessing the pore domain derived from IK were inhibited by halothane, whereas those possessing the SK1 pore domain were insensitive. Time constants of inhibition by halothane were significantly smaller in the outside-out patches than in the inside-out patches of both wild-type IK and a chimera with pore domain of IK. 相似文献
Methods: R- and S-enantiomers as well as racemic mixtures of both agents were tested in concentrations of 1, 5, 10, and 15 mm. Saponin-skinned muscle fibers from the extensor digitorum longus muscle of BALB/c mice were examined according to a standardized procedure. For the assessment of effects on Ca2+ uptake and release from the sarcoplasmic reticulum, agents were added to the loading solution and the release solution, respectively, and force and Ca2+ transients were monitored.
Results: The effects of S-enantiomers on both Ca2+ release and reuptake were significantly more pronounced than those of racemic mixtures and R-enantiomers, respectively. In addition, the effects of racemates were markedly stronger than those of R-enantiomers. With regard to Ca2+ release, the effects of bupivacaine isomers were more pronounced than the isomers of ropivacaine. 相似文献
Methods: Perfused attached human neuroblastoma SH-SY5Y cells were exposed to carbachol (1 mm, 2 min) in the absence and presence of isoflurane (1 mm) and in the absence and presence of extracellular Ca2+ (1.5 mm). The authors studied the effect of the nonspecific cationic channel blocker La3+ (100 [mu]m), of the L-type Ca2+ channel blocker nitrendipine (10 [mu]m), and of the N-type Ca2+ channel blocker [omega]-conotoxin GVIA (0.1 [mu]m) on isoflurane modulation of the carbachol-evoked [Ca2+]cyt transient. [Ca2+]cyt was detected with fura-2 and experiments were carried out at 37[degrees]C.
Results: Isoflurane reduced the peak and area of the carbachol-evoked [Ca2+]cyt transient in the presence but not in the absence of extracellular Ca2+. La3+ had a similar effect as the removal of extracellular Ca2+. [omega]-Conotoxin GVIA and nitrendipine did not affect the isoflurane sensitivity of the carbachol response although nitrendipine reduced the magnitude of the carbachol response. 相似文献
Methods: Using Ca2+-specific confocal microfluorimetry, the anesthetic effects on Ca2+ dynamics were examined in mouse embryonic cortical neurons in association with ligand-stimulated Ca2+ influx. Studies were done at 21 [degree sign]C and 37 [degree sign]C. Mouse embryonic cortical neurons with oligodeoxyribonucleotide blockade of PMCA2 expression and transfected rat pheochromocytoma cells with blocked expression of PMCA1 were also examined.
Results: Baseline and poststimulation peak cytosolic calcium concentrations ([Ca2+]i) were increased, and Ca2+ clearance was delayed in cells exposed at 37 [degree sign]C, but not at 21 [degree sign]C, to concentrations
Methods: Vastus medialis fibers were mechanically skinned and perfused with solutions containing physiologic (1 mm) or reduced concentrations of free [Mg2+]. Sarcoplasmic reticulum Ca2+ release was detected using fura-2 or fluo-3.
Results: In MHN fibers, 1 mm halothane consistently did not induce sarcoplasmic reticulum Ca2+ release in the presence of 1 mm Mg2+. It was necessary to increase the halothane concentration to 20 mm or greater before Ca2+ release occurred. However, when [Mg2+] was reduced below 1 mm, halothane became an increasingly effective stimulus for Ca2+ release; e.g., at 0.4 mm Mg2+, 58% of MHN fibers responded to halothane. In MHS fibers, 1 mm halothane induced Ca2+ release in 57% of MHS fibers at 1 mm Mg2+. Reducing [Mg2+] increased the proportion of MHS fibers that responded to 1 mm halothane. Further experiments revealed differences in the characteristics of halothane-induced Ca2+ release in MHS and MHN fibers: In MHN fibers, at 1 mm Mg2+, halothane induced a diffuse increase in [Ca2+], which began at the periphery of the fiber and spread slowly inward. In MHS fibers, halothane induced a localized Ca2+ release, which then propagated along the fiber. However, propagated Ca2+ release was observed in MHN fibers when halothane was applied at an Mg2+ concentration of 0.4 mm or less. 相似文献
Methods: ICa was recorded from acutely isolated rat dorsal root ganglion neurons using the whole cell patch clamp technique before, during, and after application of the [mu]-opioid agonist fentanyl (0.01-1 [mu]m). Capsaicin was applied to each cell at the end of the experiment.
Results: Fentanyl reduced ICa in a greater proportion of capsaicin-responsive cells (62 of 106, 58%) than capsaicin-unresponsive cells (2 of 15, 13%;P < 0.05). Among capsaicin-responsive cells, the decrease in ICa was 38 +/- 3% (n = 36, 1 [mu]m) in fentanyl-sensitive cells versus just 7 +/- 1% (n = 15, 1 [mu]m;P < 0.05) in fentanyl-insensitive cells. Among capsaicin-responsive cells, ICa inactivated more rapidly in fentanyl-sensitive cells ([tau]h, 52 +/- 4 ms, n = 22) than in fentanyl-insensitive cells (93 +/- 14 ms, n = 24;P < 0.05). This was not due to differences in the types of Ca2+ channels expressed as the magnitudes of [omega]-conotoxin GVIA-sensitive (N-type), nifedipine-sensitive (L-type), and GVIA/nifedipine-resistant (primarily P-/Q-type) components of ICa were similar. 相似文献
Methods: In porcine ASM cells, SR Ca2+ was depleted by cyclopiazonic acid or caffeine in 0 extracellular Ca2+, nifedipine and KCl (preventing Ca2+ influx through L-type and SOCC channels). Extracellular Ca2+ was rapidly introduced to selectively activate SOCC. After SOCC activation, SR was replenished and the protocol repeated in the presence of 1 or 2 minimum alveolar concentration halothane, isoflurane, or sevoflurane. In other cells, characteristics of SOCC and interactions between acetylcholine (Ach) and volatile anesthetics were examined.
Results: Cyclopiazonic acid produced slow SR leak, whereas the caffeine response was transient in ASM cells. Reintroduction of extracellular Ca2+ rapidly increased [Ca2+]i. This influx was insensitive to nifedipine, SKF-96365, and KBR-7943, inhibited by Ni2+ and blockade of inositol 1,4,5-triphosphate-induced SR Ca2+ release, and enhanced by ACh. Preexposure to 1 or 2 minimum alveolar concentration halothane completely inhibited Ca2+ influx when extracellular Ca2+ was reintroduced, whereas isoflurane and sevoflurane produced less inhibition. Only halothane and isoflurane inhibited ACh-induced augmentation of Ca2+ influx. 相似文献
Methods: Vessels were cannulated and held at a constant transmural pressure (40 mmHg). Image analysis and microfluorimetry were used to simultaneously measure vessel diameter and smooth muscle intracellular [Ca2+] concentration ([Ca2+]i). Myosin light chain (MLC) phosphorylation was measured using the Western blotting technique.
Results: Step increases in extracellular [Ca2+] concentration (0-10 mm) in high K+ (40 mm)-depolarized smooth muscle produced incremental increases in [Ca2+]i, MLC phosphorylation, and contraction. Halothane (0.5-4.5%) inhibited contraction in a concentration-dependent manner, but the decrease in [Ca2+]i was small, and there was a marked shift in the [Ca2+]i-contraction relationship to the right, indicating an important Ca2+ desensitizing effect. Halothane (0.5-4.5%) did not affect MLC phosphorylation or the [Ca2+]-MLC phosphorylation relationship, but the MLC phosphorylation-contraction relationship was also shifted rightward, indicating an "MLC phosphorylation" desensitizing effect. In contrast, control relaxations produced by the Ca2+ channel blocker nifedipine were accompanied by decreases in both [Ca2+]i and MLC phosphorylation, and nifedipine had no affect on the [Ca2+]i-contraction, [Ca2+]i-MLC phosphorylation, and MLC phosphorylation-contraction relationships. 相似文献
Methods: The effects of sevoflurane 0-4.05% vol/vol (0-1.5 minimum alveolar concentration [MAC]) on isometric and isotonic variables of contractility and on the intracellular calcium transient were assessed in isolated ferret right ventricular papillary muscles microinjected with the Ca2+-regulated photoprotein aequorin. The intracellular calcium transient was analyzed in the context of a multicompartment model of intracellular Ca2+ buffers in mammalian ventricular myocardium.
Results: Sevoflurane decreased contractility, time to peak force, time to half isometric relaxation, and the [Ca2+]i transient in a reversible, concentration-dependent manner. Increasing [Ca2+]o in the presence of sevoflurane to produce peak force equal to control increased intracellular Ca2+ transient higher than control. 相似文献
Methods: Experiments were conducted using the outside-out configuration of the patch-clamp method applied to enzymatically prepared peripheral nerve fibers of Xenopus laevis. Half-maximal inhibiting concentrations were determined for Na+ channels and different K+ channels by nonlinear least-squares fitting of concentration-inhibition curves, assuming a one-to-one reaction.
Results: Externally applied meperidine reversibly blocked all investigated channels in a concentration-dependent manner, i.e., voltage-activated Na+ channel (half-maximal inhibiting concentration, 164 [mu]M), delayed rectifier K+ channels (half-maximal inhibiting concentration, 194 [mu]M), the calcium-activated K+ channel (half-maximal inhibiting concentration, 161 [mu]M), and the voltage-independent flicker K+ channel (half-maximal inhibiting concentration, 139 [mu]M). Maximal block in high concentrations of meperidine reached 83% for delayed rectifier K+ channels and 100% for all other channels. Meperidine blocks the Na+ channel in the same concentration range as the local anesthetic agent lidocaine (half-maximal inhibiting concentration, 172 [mu]M) but did not compete for the same binding site as evaluated by competition experiments. Low concentrations of meperidine (1 nM to 1 [mu]M) showed no effects on Na+ channels. The blockade of Na+ and delayed rectifier K+ channels could not be antagonized by the addition of naloxone. 相似文献