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: The dose-dependent effects of sevoflurane on angiotensin II (10-7 m)-induced contraction, the increase in intracellular Ca2+ concentration, and PKC phosphorylation of rat aortic smooth muscle were measured using an isometric force transducer, a fluorometer, and Western blotting, respectively.
Results: Angiotensin II induced a transient increase in intracellular Ca2+ concentration, phosphorylation of Ca2+-dependent PKC (cPKC)-[alpha], and consequently, a transient contraction of rat aortic smooth muscle. Phosphorylation of the Ca2+-independent PKC-[epsilon] was not detected. The angiotensin II-induced contraction was almost completely abolished by removing extracellular Ca2+ and was significantly inhibited by the selective cPKC inhibitor Go 6976 (10-5 m) but was not inhibited by the nonselective PKC inhibitor Ro 31-8425 (10-5 m). Sevoflurane dose-dependently inhibited the angiotensin II-induced contraction, with reductions of 14.2 +/- 5.2% (P > 0.05), 26.7 +/- 8.9% (P < 0.05), and 38.5 +/- 12.8% (P < 0.01) (n = 10) in response to 1.7, 3.4, and 5.1% sevoflurane, respectively. The angiotensin II-elicited increase in intracellular Ca2+ concentration was not significantly influenced by 3.4, 5.1, or 8.5% sevoflurane. However, cPKC-[alpha] phosphorylation induced by angiotensin II was inhibited dose dependently by 1.7, 3.4, and 5.1% sevoflurane, with depressions of 20.5 +/- 14.2% (P > 0.05), 37.0 +/- 17.8% (P < 0.05), and 62.5 +/- 12.2% (P < 0.01) (n = 4), respectively. 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: [Ca2+]i was monitored by measuring the 500-nm light emission ratio (F340/F380) of a Ca2+ indicator fura-2 with isometric tension of canine tracheal smooth muscle strip. During Ca2+-free conditions, carbachol (10-5 M) was introduced with pretreatment of halothane (0-3%). During Ca2+-free conditions, 20 mM caffeine, a Ca (2+-induced) Ca2+ release channel opener, was introduced with or without halothane. We measured [IP3]i during exposure to carbachol and halothane by radioimmunoassay technique.
Results: Pretreatment with halothane significantly diminished carbachol-induced increases in [Ca2+]i by 77% and muscle tension by 83% in a dose-dependent manner. Simultaneous administration of halothane significantly enhanced caffeine-induced transient increases in [Ca2+] (i) and muscle tension in a dose-dependent manner, by 97% and 69%, respectively. Pretreatment with halothane abolished these responses. Rapid increase in [IP3]i produced by carbachol was significantly inhibited by 32% by halothane in a dose-dependent manner. 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: Freshly isolated rat ventricular myocytes were loaded with the Ca2+ indicator, fura-2, and placed on the stage of an inverted fluorescence microscope in a temperature-regulated bath. [Ca2+]i (340/380 ratio) and myocyte shortening (video-edge detection) were monitored simultaneously in individual cells field-stimulated at 0.3 Hz. Amplitude and timing of myocyte shortening and [Ca2+]i were compared before and after addition of thiopental. Intracellular pH was measured with the pH indicator, BCECF (500/440 ratio). Real-time uptake of Ca2+ into isolated sarcoplasmic reticulum vesicles was measured using fura-2 free acid in the extravesicular compartment. One hundred thirty-two cells were studied.
Results: Field stimulation increased [Ca2+]i from 85 +/- 10 nM to 355 +/- 22 nM (mean +/- SEM). Myocytes shortened by 10% of resting cell length (127 +/- 5 [micro sign]m). Times to peak [Ca2+]i and shortening were 139 +/- 6 and 173 +/- 7 msec, respectively. Times to 50% recovery for [Ca2+]i and shortening were 296 +/- 6 and 290 +/- 6 ms, respectively. Addition of thiopental (30-1,000 [micro sign]M) resulted in dose-dependent decreases in peak [Ca2+]i and myocyte shortening. Thiopental altered time to peak and time to 50% recovery for [Ca2+]i and myocyte shortening and inhibited the rate of uptake of Ca2+ into isolated sarcoplasmic reticulum vesicles. Thiopental did not, however, alter the amount of Ca2+ released in response to caffeine in sarcoplasmic reticulum vesicles or intact cells. Thiopental (100 [micro sign]M) increased intracellular pH and caused an upward shift in the dose-response curve to extracellular Ca2+ for shortening, with no concomitant effect on peak [Ca2+]i. These effects were abolished by ethylisopropyl amiloride, an inhibitor of Na+ -H+ exchange. 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: 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: 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: The effect of 0.5-3% isoflurane was studied (1) on AngII (10-6 m)-induced intracellular Ca2+ mobilization, intracellular Ca2+ release from internal stores, and Ca2+ influx in Fura-2 loaded cultured aortic vascular smooth muscle cell isolated from 6-week-old Wistar Kyoto and spontaneously hypertensive rats, using fluorescent imaging microscopy; and (2) on the organization of cytoskeletal elements, using immunofluorescence labeling.
Results: In both stains, isoflurane decreased in a concentration-dependent manner AngII-induced intracellular Ca2+ mobilization, Ca2+ release from internal stores, and Ca2+ influx through nifedipine-insensitive Ca2+ channels. This effect occurred at a lower concentrations of isoflurane in Wistar Kyoto rats than in spontaneously hypertensive rats. In both strains, the effect of isoflurane on AngII- Ca2+ mobilization was abolished by impairment with nocodazole, vinblastine, or paclitaxel of microtubules polymerization. Isoflurane directly altered tubular network organization in a concentration-dependent and reversible manner. 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: Canine PV rings with endothelium (E+) and without endothelium (E-) were isolated for measurement of isometric tension. The effects of ketamine (10-5 m~10-3 m) on acetylcholine contraction were assessed in E+ and E- rings. The effects of inhibiting nitric oxide synthase on ketamine-induced changes in acetylcholine contraction were investigated in E+ rings, whereas the effects of Ca2+ influx and Ca2+ release were investigated in E- rings. In fura-2 loaded E- PV strips, the effects of ketamine (10-4 m) on the intracellular Ca2+ concentration-tension relation (i.e., myofilament Ca2+ sensitivity) were assessed in the presence or absence of acetylcholine. The roles of the protein kinase C and rho-kinase signaling pathways in ketamine-induced changes in myofilament Ca2+ sensitivity were also investigated.
Results: Ketamine caused dose-dependent (P < 0.001) inhibition of acetylcholine contraction in E+ and E- PV rings. The ketamine-induced attenuation of acetylcholine contraction was still observed after inhibition of nitric oxide synthase (P = 0.002), Ca2+ influx (P < 0.001), and Ca2+ release (P = 0.021). Ketamine alone had no effect on myofilament Ca2+ sensitivity (P = 0.892) but attenuated (P = 0.038) the acetylcholine-induced increase in myofilament Ca2+ sensitivity. This attenuation was still observed after rho-kinase inhibition (P = 0.039), whereas it was abolished by protein kinase C inhibition (P = 0.798). 相似文献
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: 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: Freshly isolated myocytes were loaded with fura-2 and field stimulated (0.3 Hz) at 28 [degree sign]C. Amplitude and timing of intracellular Ca2+ concentration (at a 340:380 ratio) and myocyte shortening (video edge detection) were monitored simultaneously in individuals cells. Real time Ca2+ uptake into isolated sarcoplasmic reticulum vesicles was measured using fura-2 free acid in the extravesicular compartment.
Results: The authors studied 120 cells from 30 rat hearts. Fentanyl (30-1,000 nm) caused dose-dependent decreases in peak intracellular Ca2+ concentration and shortening, whereas morphine (3-100 [micro sign]M) decreased shortening without a concomitant decrease in the Ca2+ transient. Fentanyl prolonged the time to peak and to 50% recovery for shortening and the Ca2+ transient, whereas morphine only prolonged the timing parameters for shortening. Morphine (100 [micro sign]M), but not fentanyl (1 [micro sign]M), decreased the amount of Ca2+ released from intracellular stores in response to caffeine in intact cells, and it inhibited the rate of Ca2+ uptake in isolated sarcoplasmic reticulum vesicles. Fentanyl and morphine both caused a downward shift in the dose-response curve to extracellular Ca2+ for shortening, with no concomitant effect on the Ca2+ transient. 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: In enzymatically dissociated porcine ASM cells imaged using fluorescence microscopy, sarcoplasmic reticulum Ca2+ was depleted by 1 [mu]m cyclopiazonic acid in 0 extracellular Ca2+, nifedipine, and potassium chloride (preventing Ca2+ influx through L-type channels and SOCE). Extracellular Ca2+ was rapidly reintroduced to selectively activate SOCE in the presence or absence of 1 minimum alveolar concentration (MAC) halothane, isoflurane, or sevoflurane. Anesthetic interference with SOCE regulation by cyclic nucleotides was examined by activating SOCE in the presence of (1) 1 [mu]m acetylcholine, (2) 100 [mu]m dibutryl cyclic adenosine 3',5'-cyclic monophosphate, or (3) 100 [mu]m 8-bromo-cyclic guanosine 3',5'-cyclic monophosphate.
Results: SOCE was enhanced by acetylcholine, whereas volatile anesthetics and both cyclic nucleotides partially inhibited Ca2+ influx. Preexposure to 1 or 2 MAC anesthetic (halothane > isoflurane > sevoflurane) inhibited SOCE. Only halothane and isoflurane inhibited acetylcholine-induced augmentation of Ca2+ influx, and significantly potentiated cyclic nucleotide inhibition such that no influx was observed in the presence of anesthetics and cyclic nucleotides. 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: 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