Phospholipid composition and Ca2+ uptake properties of plasma membrane isolated from canine stomach smooth muscle

The Ca2+ uptake and phospholipids influencing it in plasma membrane isolated from canine stomach smooth muscle was investigated. The major phospholipids in plasma membrane were phosphatidylethanolamine (PE, 26%), phosphatidylcholine (PC, 20%) and phosphatidylserine + phosphatidylinositol (PS + PI, 15%). The cholesterol/phospholipid ratio in the membrane was 0.64. ATP-dependent Ca2+ uptake was inhibited by exogenous PE, PC and PS, but increased by PI. Saponin and phospholipase C inhibited ATP-dependent Ca2+ uptake and accelerated release of Ca2+ from actively loaded plasma membrane vesicles. In the absence of ATP, PE slightly and PI significantly increased Ca2+ uptake, but PC and PS did not affect the Ca2+ uptake. Release of Ca2+ from actively loaded vesicles was 5 times greater in the presence of PI than in its absence. Results suggest PI to be the most active of the tested phospholipids in influencing Ca2+ movement across plasma membrane.     

Myosin B ATPase activity of the intestinal smooth muscle in intestinal obstruction

Intestinal smooth myosin B was prepared from muscle layers around the lesion in dogs with experimental colonic stenosis and in patients with congenital intestinal obstruction. Mg2+-ATPase activity of the myosin B was compared between the proximal dilated segment and distal segment to obstruction. Experimental colonic stenosis: In early period after surgery, proximal colons showed higher activity of myosin B ATPase than distal colons, decreasing to less than distal colon as time passed. Congenital intestinal obstruction: In three cases, whose atresia might have occurred at earlier period of gestation, proximal bowels showed less activity of myosin B ATPase than distal bowels. However, in two cases, whose atresia might have occurred at later period of gestation, and two cases with intestinal stenosis, proximal bowels indicated higher activity of myosin B ATPase than distal bowels. These data suggested that the contractibility of the proximal intestine was depending on the duration of obstruction, and it was depressed in the former patients and was accelerated in the latter patients. These results suggested that the extensive resection of dilated proximal bowel in the congenital atresia is not always necessary to obtain good postoperative intestinal dynamics at the operation of the atresial lesions which may be induced at later period of gestation. They also suggested that surgery for intestinal obstruction should be performed before the depression of intestinal contractibility to get good bowel function.     

胃平滑肌肿瘤的诊断与治疗

胃平滑肌肿瘤有良、恶性之分。主要临床特征为腹痛、腹部包块、呕血或黑便。本病多发生于40岁以上中年人。X线钡餐造影、胃镜、B超、CT等检查相结合，可以提高诊断率。现就我院近25年来收治经手术病理证实的21例胃平滑肌肿瘤作一回顾性分析。并就该病的发病概况、临床特征、临床表现、诊断和治疗等问题予以讨论。     

The role of phospholipase C and phosphatidylinositol 3-kinase in vascular smooth muscle cell migration and proliferation

BACKGROUND: Vascular smooth muscle cell (SMC) proliferation and migration both contribute to the formation of intimal hyperplasia. Phospholipase C (PLC) and phosphatidylinositol 3-kinase (PI3-K) are ubiquitous signaling proteins that mediate multiple cellular events. In this study, we investigate the role of PLC and PI3-K in platelet-derived growth factor (PDGF) and extracellular matrix protein (ECM) induced SMC proliferation and migration. MATERIAL AND METHODS: Proliferation of human saphenous vein SMC was assessed by (3)H-thymidine incorporation. SMC migration was evaluated using a microchemotaxis chamber. U-73122 was used as a general inhibitor for PLC, and D609 and ET-18-OCH3, respectively, were used to block the isotypes of PLC, phosphatidylcholine- (PC-), and phosphatidylinositol- (PI-) specific PLC. PI3-K activity was inhibited using two selective inhibitors, LY-294002 and wortmannin. RESULTS: PDGF and Type 1 collagen (CN-I) stimulated SMC proliferation, whereas PDGF and four distinct extracellular matrix proteins CN-I, Type 4 collagen (CN-IV), fibronectin (FN), and laminin (LN) stimulated SMC migration. Both isotypes of PLC as well as PI3-K were necessary for PDGF- and CN-I-induced proliferation. Signaling for migration, however, was more specific. Of the various signaling proteins studied, only PI-PLC was necessary for PDGF-induced SMC migration. Conversely, PI3-K was the only signaling protein necessary for SMC migration in response to ECM proteins. CONCLUSION: The signaling pathways necessary for PDGF- and CN-I-induced SMC proliferation involve both isotypes of PLC as well as PI3-K. The signaling pathways used by growth factors and ECM to stimulate SMC migration are more selective. Understanding the intracellular signaling pathways required for SMC proliferation and migration may allow the development of tools to selectively block intimal hyperplasia.     

胃平滑肌肿瘤的临床与病理分析

目的探讨胃平滑肌肿瘤的诊断、病理学特点和治疗选择 .方法对 1984年 2月至 1999年 2月经治的 45例胃平滑肌肿瘤进行回顾性分析 .结果术前确诊仅 15例 ( 33 3% ) . 45例均予手术治疗并经病理学证实 .随访中 3例因肿瘤广泛扩散而衰竭死亡 . 2例出现复发而予再次手术 ,再次手术后已分别存活 2年、 3年;其余病例随访恢复良好 .结论确立本病的诊断要根据病史、多种特殊检查的结果、肿瘤的大体形态和术中、术后病理等综合分析 .手术切除为其首选治疗方法 ,在术式选择上应根据肿瘤的部位、大小和生物学行为而定 ,一般无需行广泛的根治性胃切除 .良、恶性平滑肌肿瘤均应强调术后长期随访 ,以提高生存率 .     

异丙酚对兔离体气管平滑肌细胞内游离钙离子浓度的影响

目的 评价异丙酚对兔离体气管平滑肌细胞内游离钙离子浓度([Ca2+]i)的影响.方法 采用急性酶分离方法分离兔气管平滑肌细胞,采用随机数字表法,将细胞随机分为3组(n=5):异丙酚组(Ⅰ组,终浓度300 μmol/L)、异丙酚(终浓度300 μmol/L)+2-氨乙基硼酸二苯酯(终浓度40μmol/L)(Ⅱ组)和异丙酚(300 μmol/L)+斯里兰卡肉桂碱(终浓度10 μmol/L)(Ⅲ组).Ⅰ组加入终浓度300 μmol/L的异丙酚,孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,加入1μmol/L乙酰胆碱,记录[Ca2+]i.Ⅱ组加入终浓度40μmol/L的2-氨乙基硼酸二苯酯孵育15 min后,再加入终浓度为300μmol/L的异丙酚,与2-氨乙基硼酸二苯酯共同孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,加入1 μmol/L的乙酰胆碱.Ⅲ组加入终浓度10 μmol/L的斯里兰卡肉桂碱孵育15 min后,再加入终浓度为300μmol/L的异丙酚,与斯里兰卡肉桂碱共同孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,再加入1 μmol/L的乙酰胆碱.通过负荷钙离子荧光指示剂Fluo-3/AM测定气管平滑肌细胞内[Ca2+]i.结果 与Ⅰ组比较,Ⅱ组气管平滑肌细胞内[Ca2+]i差异无统计学意义(P＞0.05),Ⅲ组[Ca2+]i明显降低(P＜0.05).结论 异丙酚可降低兔离体气管平滑肌细胞内[Ca2+]i,其机制可能与抑制内质网1,4,5-三磷酸肌醇通路有关,而与内质网兰诺定通路无关.     

Mechanism of vascular smooth muscle cells activation by hydrogen peroxide: role of phospholipase C gamma.

BACKGROUND: Hydrogen peroxide (H2O2) formation is a critical factor in processes involving ischaemia/ reperfusion. However, the precise mechanism by which reactive oxygen species (ROS) induce vascular damage are insufficiently known. Specifically, activation of phospholipase C gamma (PLCgamma) is a probable candidate pathway involved in vascular smooth muscle cells (VSMC) activation by H2O2. METHODS: The activation of human venous VSMC was measured as cytosolic free calcium mobilization, shape change and protein phosphorylation, focusing on the role of tyrosine phosphorylation-activated PLCgamma. RESULTS: The exposure of VSMC to exogenous H2O2 caused a rapid increase in cytosolic free calcium concentration ([Ca2+]i), and induced a significant VSMC shape change. Both effects were dependent on a tyrosine kinase-mediated mechanism, as determined by the blockade of short-term treatment of VSMC with the protein tyrosine kinase inhibitor, genistein. Giving further support to the putative role of phospholipase C (PLC)-dependent pathways, the [Ca2+]i and VSMC shape change response were equally inhibited by the specific PLC blocker, 1-(6-((17-beta-methoxyestra-1,3,5(10)trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). In addition, U73122 had a protective effect against the deleterious action (24 h) of H2O2 on non-confluent VSMC. As a further clarification of the specific pathway involved, the exposure to H2O2 significantly stimulated the tyrosine phosphorylation of PLCgamma with a concentration- and time-profile similar to that of [Ca(2+)](i) mobilization. CONCLUSIONS: The present study reveals that H(2)O(2) activates PLCgamma on VSMC through tyrosine phosphorylation and that this activation has a major role in rapid [Ca(2+)](i) mobilization, shape-changing actions and damage by H(2)O(2) in this type of cells. These findings have direct implications for understanding the mechanisms of the vascular actions of H(2)O(2) and may help to design pharmacologically protective strategies.     

Ion-channel currents of smooth muscle cells isolated from the prostate of guinea-pig

OBJECTIVE: To characterize the voltage-activated ion-channel currents in guinea-pig prostate smooth muscle cells (GPSMCs). MATERIALS AND METHODS: GPSMCs were isolated using collagenase, and used in a whole-cell patch clamp study. RESULTS: When GPSMCs were dialysed with a CsCl solution all the outward K+ currents were blocked and the step-like depolarization (holding voltage -70 mV) of the cell membrane evoked inward currents that were completely blocked by nifedipine (1 micromol/L). With KCl solution, step depolarizations showed outward K+ currents composed of fast, transient outward current (Ito) and outward currents that did not inactivate. Ito was resistant to a high concentration of tetraethylammonium (TEA, 5 mmol/L) but was blocked by 4-aminopyridine (5 mmol/L). The half-activation and half-inactivation voltages of Ito were 6 mV and -58 mV, respectively. With low Ca2+ buffer (0.1 mmol/L EGTA) in the solution, there were spontaneous transient outward currents (STOCs) at depolarized membrane voltages (0 mV). STOCs were blocked by TEA (1 mmol/L) or iberiotoxin (10 nmol/L) but were insensitive to apamin (100 nmol/L). CONCLUSION: This voltage-clamp study showed that GPSMCs have l-type Ca2+ channels and more than two types of K+ channels. The voltage- and time-dependent changes of these ion channels and their interactions might be important in forming action potentials and regulating contractility.     

异丙酚对兔离体气管平滑肌舒张作用机制的研究

目的探讨异丙酚在正常和炎症状态下对气管平滑肌收缩作用的影响及其机制。方法8只健康新西兰大白兔,每次试验用气栓法处死1只,每只兔制备8个气管平滑肌条,依据悬挂气管平滑肌条的营养液中处理因素不同,采用随机数字表法将气管平滑肌条随机分为8组即（每组8个）：a组（0μmol/L）,b组（异丙酚300μmol／L）,c组（环糊精-β10mmol／L）,d组（环糊精-β10mmol／L＋异丙酚300μmol／L）,c组（0μmol／L）,f组（异丙酚300μmol／L）,g组（环糊精-β10mmol／L）,h组（环糊精-β10mmol／L＋异丙酚300μmol／L）。e,f,g,h4组气管平滑肌条浸于浓度为50μg／L肿瘤坏死因子-α溶液里,并通以95％O2和5％CO2在4℃恒温冰箱冷藏12h以供试验。用Medlab生物采集系统记录平滑肌条不同时间点张力值变化。免疫组化法测定小窝蛋白-1表达。结果与a组（1．28±0．12、1．25±0．13、1．23±0．16、1．22±0．19）比较,b组（0．86±0．13、0．61±0．11、0．51±0．17、0．51±0．18）、c组（1．18±0．15、1．08±0．13、0．98±0．15、0．89±0．16）、d组（0．98±0．12、0．84±0．14、0．80±0．14、0．78±0．17）T1。时间点张力值降低,差异有统计学意义（P〈0．05）;与b组比较c,d两组T1-4各时间点张力值高,差异有统计学意义（P〈0．05）;与e组（0．92±0．16、0．91±0．12、0．89±0．13、0．81±0．16）比较,f组（0.41±0．12、0．22±0．14、0．13±0．14、0．12±0．14）、g组（0．80±0．15、0．78±0．13、0．75±0．15、0．72±0．17）、h组（0．79±0．12、0．70±0．12、0．68±0．16、0．68±0．19）T1-4时间点张力值降低,差异有统计学意义（P〈0．05）;与f组比较g、h两组T1-4时间点张力值高,差异有统计学意义（P〈0．05）;8xe两组小窝蛋白-1为高表达;b、f两组小窝蛋白．1为低表达;c、d、g、h4组小窝蛋白-1为阴性。结论异丙酚直接舒张气管平滑肌的机制可能与其抑制小窝蛋白-1的表达有关。     

Propofol increases pulmonary artery smooth muscle myofilament calcium sensitivity: role of protein kinase C

BACKGROUND: Vascular smooth muscle tone is regulated by changes in intracellular free Ca2+ concentration ([Ca2+]i) and myofilament Ca2+ sensitivity. These cellular mechanisms could serve as targets for anesthetic agents that alter vasomotor tone. This study tested the hypothesis that propofol increases myofilament Ca2+ sensitivity in pulmonary artery smooth muscle (PASM) via the protein kinase C (PKC) signaling pathway. METHODS: Canine PASM strips were denuded of endothelium, loaded with fura-2/AM, and suspended in modified Krebs-Ringer's buffer at 37 degrees C for simultaneous measurement of isometric tension and [Ca2+]i. RESULTS: The KCl (30 mm) induced monotonic increases in [Ca2+]i and tension. Verapamil, an L-type Ca2+ channel blocker, attenuated KCl-induced increases in [Ca2+]i and tension to an equal extent. In contrast, propofol attenuated KCl-induced increases in [Ca2+]i to a greater extent than concomitant changes in tension and caused an upward shift in the peak tension-[Ca2+]i relation. Increasing extracellular Ca2+ in the presence of 30 mM KCl resulted in similar increases in [Ca2+]i in control and propofol-pretreated strips, whereas concomitant increases in tension were greater during propofol administration. The Ca2+ ionophore, ionomycin (0.1 microm), increased [Ca2+]i to approximately 50% of the value induced by 60 mm KCl. Under these conditions, propofol (10, 100 microm) caused increases in tension equivalent to 11 +/- 2 and 28 +/- 3% of the increases in tension in response to 60 mM KCl, whereas [Ca2+]i was slightly decreased. Similar effects were observed in response to the PKC activator, phorbol 12-myristate 13-acetate (PMA, 1 microm). Specific inhibition of PKC with bisindolylmaleimide I before ionomycin administration decreased the propofol- and PMA-induced increases in tension and abolished the propofol- and PMA-induced decreases in [Ca2+]i. Selective inhibition of Ca2+ -dependent PKC isoforms with G? 6976 also attenuated propofol-induced increases in tension. CONCLUSION: These results suggest that propofol increases myofilament Ca2+ sensitivity in PASM, and this effect involves the PKC signaling pathway.     

VEGF inhibits PDGF-stimulated calcium signaling independent of phospholipase C and protein kinase C

INTRODUCTION: Despite advances in both open and endovascular techniques for treatment of arterial occlusive disease, restenosis because of neointimal hyperplasia continues to be a major cause of graft failure and restenosis. This phenomenon has been attributed to vascular smooth muscle cell (VSMC) activation by several potent mitogens including platelet derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) released at the site of injury. PDGF is known to stimulate calcium influx in VSMC that has been shown to be critical for VSMC migration and proliferation. We have previously shown that VEGF inhibits PDGF-stimulated VSMC proliferation. The objective of this set of experiments was to investigate whether VEGF modulated PDGF-stimulated Ca2+ influx in VSMC. MATERIALS AND METHODS: Primary cultured human aortic SMC were grown to subconfluency and assigned to the following groups: no stimulation, stimulation with PDGF-BB (20 ng/ml), stimulation with VEGF165 (40 ng/ml), or a combination of PDGF-BB + VEGF165. Ca2+ influx was measured using a Fura-2 fluorescence assay. The intracellular Ca2+ fraction was assayed with the Fura-2 assay by using Ca2+-free media. Phospholipase Cgamma1 (PLCgamma1), protein kinase C (PKC), and Akt phosphorylation was assessed with standard immunoblotting techniques at 1, 5, and 10 min time points. Ca2+-calmodulin kinase II (CaMKII) activity was extrapolated from the phosphorylation of Phospholamban B (PLB), a well-known protein substrate, at 1, 5, and 10 min time points. RESULTS: PDGF stimulation resulted in a 328 +/- 9 nm total calcium influx in VSMC. The combination of VEGF + PDGF resulted in a 273 +/- 21 nm total calcium influx, an amount significantly less than with PDGF alone (P < 0.04). PDGF stimulation resulted in a 72 +/- 35 nm intracellular calcium release. The addition of VEGF to PDGF resulted in an intracellular calcium release of only 15 +/- 11 nm, a significant decrease compared to PDGF alone (P < 0.01). The phosphorylation of PLCgamma1, PKC, and Akt was equivalent at 1, 5, and 10 min between the PDGF and the PDGF + VEGF treatment groups. There was an increase in CaMKII activity at 1 and 5 min time points in both the PDGF and PDGF + VEGF treatment groups suggesting that extracellular calcium influx is sufficient for CaMKII activation. CONCLUSION: VEGF inhibits PDGF-stimulated total calcium influx and, in particular, PDGF-stimulated intracellular calcium release in VSMC. The equivalent phosphorylation of PLCgamma1, PKC, and Akt suggests that the inhibitory mechanism by VEGF on calcium influx occurs downstream of these proximal mediators. The inhibition of intracellular calcium release did not inhibit CaMKII activity. VEGF may play an important role in modulating PDGF induced VSMC proliferation by specifically inhibiting intracellular calcium release in response to PDGF.     

Caerulein-induced contraction of the ileal longitudinal smooth muscle isolated from various animal species

An effect of caerulein was studied on a contractile response of the ileal longitudinal smooth muscle isolated from seven animal species, monkey, dog, rabbit, guinea-pig, rat, vole and mouse. In isotonic recording, caerulein induced a contraction in the muscle isolated from all animal species. Sensitivities of ileal strips to caerulein in the contractile response was divided into three groups. That is, a high sensitive group; dog and guinea-pig, a middle sensitive group; rabbit and vole, a low sensitive group; monkey, rat and mouse. In another series of experiment, effect of several antagonists was examined on the caerulein-induced contraction in ileal muscle of dog, rabbit or guinea-pig. TTX inhibited the contractions in all the ilea. As the contraction was inhibited by atropine and scopolamine in dog ileum but not in rabbit one, the contraction may be due to an excitation of the cholinergic neuron or an excitation of non-cholinergic excitatory neuron, respectively. On the other hand, it is supposed that the contraction in guinea-pig ileum is involved to both the neurons because the contraction was inhibited partially by scopolamine and not by atropine. In conclusion, the ilea isolated from seven animal species showed species differences in sensitivity to caerulein in contractile response, and caerulein seems induces the contractions involving to different nervous systems in dog, rabbit or guinea-pig ileum, respectively.     

Myosin ATPase activity in multifidus muscle from cases of lumbar spinal derangement.

Biopsies of lumbar multifidus muscles were obtained at operation on seventeen patients aged from fifteen to fifty-eight with lumbar spinal derangement, and further material was taken from the cadavers of three subjects aged from nineteen to fifty-one. Sections were prepared to show the presence of ATPase activity, so distinguishing Fast from Slow types of muscle fibre. The normal mosiac pattern arising from the intermingling of fibres from Fast and Slow motor units was seen in sections from cadaveric material and from many of the biopsies. With age and limited lumbar flexibility, the Fast fibres became relatively smaller but with increasing variation in size, suggesting a reduced capacity for phasic activity. The presence of positive root signs was associated with a greater proportion of Slow fibres, and in some patients with the occurrence of atrophied Fast fibres, giving rise to differences in the populations of the two fibres in neighbouring fascicles. The results suggest that multifidus adopts an increasingly postural role with advancing age and with disabling lesions of the lumbar spine.     

Studies on isolated smooth muscle cells. IX. Application of papain for isolation of single smooth muscle cells from guinea-pig taenia coli

To prepare single smooth muscle cells from the taenia coli of guinea pig, the application of papain to the enzymatic solution was examined under two conditions: 1) the isolation in a modified Tyrode solution (containing 0.18 mM Ca2+: 0.18 mM Ca2+-Tyrode solution) and 2) the isolation in a high-K+ Tyrode solution (Na+ was replaced by K+, and Ca2+ was not added: high-K+ Tyrode solution). The presence of papain during collagenase digestion reduced contamination of broken cells and cell debris. In the case of the high-K+ Tyrode solution, papain increased the yield of single cells significantly. The cells were contracted in a dose-dependent manner by Ca2+ in the high-K+ Tyrode solution and by carbachol in 0.18 mM Ca2+-Tyrode solution; furthermore, the contractions were antagonized by verapamil and atropine, respectively. Treatment with papain did not affect cell sensitivity to the stimulants. Therefore, our results suggest that the addition of papain is useful for the isolation of single cells to investigate the physiological and pharmacological characteristics of smooth muscle.     

Effects of calcium and verapamil on vesicourethral smooth muscle of rabbits

Isolated smooth muscle strips from the rabbit bladder body, bladder base, and proximal urethra were contracted with ionic calcium (Ca2+) alone and with the calcium-selective ionophore A23187, acetylcholine, norepinephrine, adenosine triphosphate (ATP), and direct electrical stimulation. The effects of Ca2+ and the calcium entry blocker verapamil on spontaneous muscle activity and on contractions induced by these agonists were examined. Ca2+ -free Tyrode's solution and verapamil, 1 x 10(-7)M and above, relaxed all of the vesicourethral smooth muscle strips. In addition verapamil, 1 x 10(-8) to 1 x 10(-6) M depending on the particular stimulant employed, noncompetitively inhibited smooth muscle contractions elicited by Ca2+, acetylcholine, norepinephrine, ATP, and direct electrical stimulation. It was concluded that transmembrane Ca2+ influx was important not only in the maintenance of tone and spontaneous phasic muscle activity, but also for the activation of contractions induced by all of the stimulants tested. The data also suggest that intracellular Ca2+ fraction(s) participate in the contractile responses to acetylcholine and norepinephrine challenge, but not to contractions evoked by ATP or electricity.     

Effects of ketamine on K+-contracture in isolated vascular smooth muscle from rabbit

The effects of ketamine on contraction induced by depolarization of cell membrane (high K+-induced contracture) were studied in isolated vascular smooth muscle from rabbit portal vein. Ketamine in concentrations above 5 x 10(-4) M caused relaxation in phasic contraction, and above 10(-4) M caused relaxation in tonic contraction. These effects of ketamine at concentrations of between 10(-5) to 10(-3) M were dose dependent and reversible. In concentration above 10(-5) M, ketamine decreased the contractile response (tonic contraction) induced by 2.5 mM Ca2+ after the temporary contracture in Ca2+-free, high K+ solution. The contractile responses to norepinephrine (10(-6) M) or serotonin (10(-6) M) were also inhibited by ketamine. From these findings, it is concluded that ketamine decreases contractile responses due to transmembrane Ca2+ influx after depolarization of cell membrane and may decrease the contractile responses in concentration above 5 x 10(-4) due to Ca2+ release inhibition from sarcoplasmic reticulum.     

异丙酚对哮喘豚鼠离体气管平滑肌张力的作用

目的 探讨异丙酚对哮喘豚鼠离体气管平滑肌张力的作用及其作用机制。方法 48只健康豚鼠随机分为哮喘组(n=28)和正常组(n=20),卵蛋白致敏法建立哮喘豚鼠模型,每只豚鼠制备5-7个气管平滑肌环,依据悬挂平滑肌环的营养液中处理因素不同将气管平滑肌环随机分为control亚组、10％Intralipid亚组、10、30、100、300μmol/L Propofol亚组,通过与气管环相连的力-位移换能器记录其张力变化,采用悬挂平滑肌环的营养液中无Ca2+的方法测定异丙酚对Ryanodine受体介导的细胞内Ca2+释放的影响。结果 (1)100μmol/L异丙酚显著舒张哮喘豚鼠静息气管平滑肌。四种浓度异丙酚对乙酰胆碱所致气管平滑肌收缩呈剂量依赖的舒张作用。(2)四种浓度异丙酚预适应可剂量依赖性抑制乙酰胆碱所致气管平滑肌收缩。哮喘组30μmol/L异丙酚预适应使乙酰胆碱所致的气管平滑肌依内钙性收缩由(37.7±2.8)％降为(27.7±1.9)％,依外钙性收缩由(62.3±4.5)％降为(51.5±3.5)％,与control亚组比较差异有显著性(P<0.01)。(3)四种浓度异丙酚抑制乙酰胆碱所致气管平滑肌依内钙性收缩作用,与无Ryanodine作用组比较,差异无显著性(P>0.05)。结论临床相关浓度异丙酚预适应显著抑制乙酰胆碱收缩哮喘豚鼠离体气管平滑肌的作用,其作用机制与Rvanodine受体介导     

The role of intracellular and extracellular calcium in mechanical and intracellular electrical activity of human urinary bladder smooth muscle

We studied the role of extracellular and intracellular Ca²⁺ in human detrusor smooth muscle contraction. Simultaneous recordings of mechanical and intracellular electrical activity were made in three different Ca²⁺ concentrations: normal Krebs' solution (100%), 10% of the standard Ca²⁺ concentration and a solution in which Ca²⁺ was omitted from the medium (0%). Spontaneous contractions and KCl or CCh induced contractions were studied. Ryanodine and caffeine were used to manipulate the intracellular Ca²⁺ stores. The present results show that only a very small amount of Ca²⁺ in the extracellular space is sufficient to support spontaneous and induced contractions. Spike-shaped potentials and long lasting depolarisations were recorded in all three solutions. However, the prevalence of long lasting depolarisations increased when the extracellular Ca²⁺ concentration was reduced. The amplitude of the spike-shaped potentials and long lasting depolarisations appeared to be negatively affected by diminishing the extracellular Ca²⁺ concentration. Additionally, the duration of the long lasting depolarisations was reduced in 0% Ca²⁺. The contraction upon KCl stimulation was primarily depending on the extracellular Ca²⁺. Upon muscarinic receptor stimulation, a combined activation of Ca²⁺ mobilisation from intracellular and extracellular stores may occur; the ratio of contribution of these two sources changes in accordance with the requirements of the conditions. Received: 1 December 1999 / Accepted: 1 March 2000