Effect of tri-o-cresyl phosphate and methamidophos on Ca uptake by brain synaptosomes in hens

The effect of tri-o-cresyl phosphate (TOCP) and methamidophos (MET) on potassium-stimulated ⁴⁵Ca uptake by brain synaptosomes in hens was studied. An in vivo test showed that TOCP increased potassium-stimulated calcium uptake 2 h after its administration, but that verapamil suppressed the enhancement of this calcium uptake. An in vitro test showed that lower concentrations of TOCP stimulated calcium uptake by synaptosomes, but that higher concentrations inhibited the uptake. In contrast, all tested concentrations of MET obviously inhibited calcium uptake; however, since calcium uptake was decreased by the administration of verapamil plus either TOCP or MET, the mechanism by which TOCP affects the voltage-operated calcium channel may be different from that of MET. The disruption of calcium homeostasis may be involved in organophosphate-induced delayed neurotoxicity (OPIDN). Calcium channel blocker may ameliorate OPIDN by maintaining calcium homeostasis in nerve cells.     

SHR大鼠心室肌细胞分离方法改进及其L-型钙电流的观察

文章探索建立简单可靠的SHR大鼠心室肌细胞的分离方法,提高细胞存活率和膜片钳试验成功率。采用Langendorff灌流装置,离体心脏逆向灌流,分离单个SHR大鼠心室肌细胞。使用膜片钳全细胞记录技术,记录大鼠心室肌细胞L-型钙电流。通过对细胞的观察发现,细胞呈长杆状,横纹清晰,细胞膜结构完整。膜片钳全细胞记录到典型的L-型钙电流,激活电位-40 mV,峰值电位0 mV,反转电位+50～+60 mV,呈现出电压依赖性。观察到的L-型钙电流可被钙通道阻滞剂维拉帕米抑制。结果表明,采用的大鼠心肌细胞分离方法可分离制备出适合膜片钳电生理观察的心肌细胞标本。     

Development of multidrug resistance in a canine lymphoma cell line

New multidrug resistant cell lines developed from the canine B cell lymphoma cell line (GL-1) were characterized in terms of chemosensitivity to some antineoplastics and P-glycoprotein (Pgp) expression. GL-1 was continuously exposed to a culture medium containing gradually increasing levels of doxorubicin and the cells that could grow in the presence of doxorubicin were obtained. Chemosensitivity of these cells to various antineoplastics were investigated with or without verapamil, which reversed Pgp-mediated drug resistance. The expression of Pgp on the cells was also examined by Western blot analysis. As a result, three kinds of resistant cell lines, designated as GL-DOX60, 300, and 4000 were obtained. These cell lines showed stable proliferation in the medium containing 60, 300, and 4000 ng/ml, respectively. These cells were much more resistant to vincristine than doxorubicin. This resistance was strongly reversed by the presence of verapamil. On the other hand, cisplatin was effective enough in killing these derived cells. In the Western Blot analysis, some bands that reacted to the anti-human Pgp monoclonal antibodies were observed in GL-DOX4000. The cells derived from GL-1 have multidrug resistance potential mediated by canine Pgp. The cells produced in this experimental trial are considered to be useful models for various investigations on canine multidrug resistance.     

Mechanisms by which verapamil protects against lipopolysaccharide-induced pancreatic acinar cell damage in vitro

AIM:To investigate the protective effect of verapamil (Vera) on lipopolysaccharide (LPS)-induced pancreatic acini damage and its mechanism. METHODS:Rat pancreatic acinar cells were isolated by collagenase digestion and were pre-treated with Vera (50 mg/L, 100 mg/L), then exposed to LPS (10 mg/L) or normal culture media, respectively. At various time points (30 min, 1 h, 2 h, 4 h, 10 h) after treatment of the agents, cell viability was determined by MTT and supernatant of cell culture was collected to measurer the content of maloidialdehyde (MDA), the activity of superoxide dismutase (SOD) and phospholipase (PLA2). Some cells were loaded with Fluo-3/AM, and the dynamic change of ［Ca2+］i in single pancreatic acinar cell was determined by laser scanning confocal microscopy. RESULTS:Vera attenuated LPS-induced cell damage (P<0.05) and inhibited the elevation of cytosolic free calcium in rat pancreatic acinar cells. In the supernatant, Vera decreased the content of MDA and the activity of PLA2 (P<0.05) and increased the activity of SOD (P<0.05). CONCLUSION:Vera attenuates LPS-induced cell damage by blocking calcium overload, inhibiting superoxidative response, decreasing activity of pancreatic enzyme, and hence plays a protective effect on pancreatic acinar cells.     

两种钙拮抗剂对肉鸡PHS的影响

探讨了两种钙拮抗剂(Calcium Antagonists,CA)对肉鸡肺动脉高(Pulmonary Hypertension Syndrome,PHS)的影响,从而较深层地揭示了肉鸡肺动脉高压的形成机理,为预防和治疗肉鸡腹水综合征(Ascites Syndrome.AS)提供理论依据.结果表明:在28和36日龄,硝苯地平与低温组比降低平均肺动脉压(mean Pulmonary Artery Pressure,mPAP),在0.05水平有差异;在44日龄,低温组为3.7kPa±0.7 kPa,硝苯地平组为2.4kPa±0.2 kPa,硝苯地平组mPAP低于低温组,在0.01水平有差异;硝苯地平降低AS的发生率,在0.05水平上有差异.在28和36日龄低温组mPAP为3.4 kP±0.7 kPa和3.4 kPa±1.3 kPa.维拉帕米组mPAP为1.8 kPa±0.8 kPa和1.3 kP±0.3kPa,与低温组比维拉帕米降低mPAP,在0.05水平有差异;44日龄维拉帕米组mPAP低于低温组,在0.01水平有差异.维拉帕米明显降低AS的发生率(P＜0.05).试验结果显示,维拉帕米和硝苯地平降低了低温诱发肺动脉高压和AS的发生率.初步证实钙信号参与了肺动脉高压的形成,对研究AS的发生发展具有重要意义.     

Effects of calmodulin antagonist and slow calcium channel antagonist on reperfusion injury of isolated rat hearts in calcium paradox

AIM: To observe the protective effect of calmodulin antagonist trifluoperazine(TFP) and slow calcium channel antagonist verapamil (VP) upon calcium overload injury. METHODS: The calcium content of the myocardium, lactate dehydrogenase (LDH) release, protein loss and coronary flow were measured after the isolated rat hearts were perfused by TFP and VP. RESULTS: TFP could significantly reduce the tissue calcium , LDH release and protein loss of the myocardium ( P <0.01) while VP had no such effects.The above indexes were further reduced when TFP and VP were used simutaneously( P <0.01).CONCLUSION:TFP can effectively alleviate the severity of the myocardium injury during calcium paradox while VP has no such effects.The simultanous use of VP and TFP is more effective in preventing tissue damage of the heart than the use of TFP alone.The massive influx of Ca²⁺ in calcium paradox is mainly a calmodulin related process.     

Teratogenic and cytogenetic effects of ivermectin and its interaction with P-glycoprotein inhibitor

Experiments in animals proved that P-glycoprotein (Pgp) forms a functional barrier between maternal and fetal blood circulation in the placenta, thus protecting the fetus from exposure to xenobiotics during pregnancy. In this study we aimed to demonstrate the effects of administration of ivermectin (anthelmentic drug, Pgp substrates), either alone or simultaneously with verapamil (Pgp inhibitor) in Wister rats on fetal development, maternal bone marrow for detection of micronuclei (MN), chromosomal aberrations and mitotic index (MI) and embryonic liver cells for cellular proliferation indicated by MI, and bleeding from umbilical vessels for detection of embryonic micronuclei (MN). The results revealed that administration of ivermectin or verapamil at 6th through 15th day of gestation did not significantly altered fetal development. While, co-administration of ivermectin and verapamil clearly disturbed fetal development as indicated from abnormal feto-maternal attachment and a significant decrease in fetal weights and numbers. Furthermore, co-administration of both drugs induced a significant increase in resorption sites, post-implantation loss and external, visceral and skeletal abnormalities. They also induced genotoxicity in both dam and embryonic cells indicated by reduced mitotic index, increased number of micronucleated erythrocytes in both, and increased different types of chromosomal aberrations in dam cells, while ivermectin alone show some genotoxic effect on somatic cells of dams and the embryos. Verapamil induced reduction of embryonic mitotic index. We concluded combined treatment of ivermectin and verapamil severely affect fetal genetic material and development and induced genotoxic effect in somatic cells of the dams.     

维拉帕米对脊尾白虾体内恩诺沙星代谢及消除的影响

为了解维拉帕米对恩诺沙星在脊尾白虾体内代谢及消除的影响,在水温(18.1±0.5)℃条件下,对照组每天以10mg/kg体重剂量连续7天投喂脊尾白虾恩诺沙星,维拉帕米组在投喂恩诺沙星的同时以4 mg/L剂量药浴脊尾白虾维拉帕米,比较了维拉帕米组和对照组中恩诺沙星及其代谢物环丙沙星的浓度变化与消除动力学统计矩参数。结果显示,肝胰腺、肌肉、和鳃3种组织中的恩诺沙星浓度均随时间呈规律性递减,维拉帕米组3种组织中的恩诺沙星浓度、AUC和t1/2β均高于对照组(P0.05),而维拉帕米组各组织中的环丙沙星的浓度和AUC却显著低于对照组(P0.05);维拉帕米组3种组织中恩诺沙星和环丙沙星的β、CL均显著小于对照组(P0.05)。结果表明,维拉帕米抑制了脊尾白虾体内恩诺沙星的代谢及消除速率。     

Effects of Ca2+on the releases of ET-1, NO and PGI2 from bovine coronary artery endothelial cells during hypoxia

AIM: To explore the mechanism of ET-1, NO and PGI² release from coronary artery endothelial cells(CAEC) induced by acute hypoxia. METHODS: Bovine coronary artery endothelial cells were cultured and [⁴⁵ Ca²⁺] was used to investigate the difference of calcium uptake between normoxia group and hypoxia group(3% O₂). The contents of ET-1, NO and PGI² in media of normoxia group, hypoxia group and hypoxia + verapamil group were measured 24 h after hypoxia. RESULTS: [ ⁴⁵ Ca²⁺] uptake by CAEC in hypoxia group was 1.9 times more than normoxia group(P< 0.01). Hypoxia + verapamil group released more PGI², ET-1 and less NO than hypoxia group(P< 0.05). CONCLUSION: Changes of ET-1, NO and PGI² releases during hypoxia may be caused by the inflow of Ca²⁺ into coronary artery endothelial cells.