褪黑激素对大脑皮层谷氨酸释放及其神经毒的拮抗作用

AIM: To observe the effects of melatonin (Mel) on glutamate (Glu) release from the cortical synaptosomes in old mice and on neurotoxicity induced by KCl, Glu in cultured cortical cells of fetal rat and to explore the antiaging mechanism of Mel. METHODS: Glu release by the synaptosomes in old mouse cerebral cortex was detected in a spectrofluorophotometer. The neuronal viability in primary cultures from rat cerebral cortex was assessed using MTT stain and lactate dehydrogenase (LDH) efflux in the bathing medium. RESULTS: Mel inhibited the K+ (30 mmol.L-1)-induced Glu release from synaptosomes either in calcium dependent or independent conditions [control (10.6 +/- 1.1), (9.2 +/- 0.7) mumol.g-1 (protein); Mel 0.1 mumol.L-1 (6.5 +/- 0.9), (7.5 +/- 0.6) mumol.g-1 (protein), respectively, P < 0.01 vs control group), increased MTT activity (control 0.67 +/- 0.04, 0.81 +/- 0.03; Mel 0.1 mumol.L-1 0.715 +/- 0.023, 0.925 +/- 0.027, P < 0.01 vs control group] and decreased LDH efflux (control 0.400 +/- 0.016, 0.379 +/- 0.016; Mel 0.1 mumol.L-1 0.345 +/- 0.021, 0.340 +/- 0.012, respectively, P < 0.01 vs control group), therefore, protected the neuronal viability against KCl and Glu-induced injury. CONCLUSION: The inhibitory effect of Mel on Glu release from cortical synaptosome and the protective effect of Mel on cortical neurons against neurotoxicity are its antiaging mechanisms.     

腺苷的血管效应与腺苷三磷酸敏感性钾通道的关系

目的 研究大鼠主动脉腺苷受体和腺苷三磷酸（ＡＴＰ）敏感性钾通道间的关系。方法 在离体大鼠主动脉上观察内皮完整和内皮去除后腺苷受体介导的血管效应及吡那尔与格列苯脲对腺苷作用的影响。结果：腺苷３－３００μｍｏｌ．Ｌ＾－１浓度依赖地松弛ＫＣｌ２０ｍｍｏｌ．Ｌ＾－１预收缩的离体大鼠主动脉环,在４８／９９的标本,腺苷产生先短暂收缩后持续舒张的双向反应,格列本脲１和１００μｍｏｌ．Ｌ＾－１阻断ＡＴＰ敏感性通道     

Effects of KATP channel modulation on myocardial glycogen content, lactate, and amino acids in nonischemic and ischemic rat hearts

ATP-sensitive potassium (KATP) channels are involved in the mechanisms underlying ischemic preconditioning. KATP channels open during ischemia, presumably secondary to intracellular metabolic alterations. The direct effects of KATP channel modulation on myocardial metabolism have not been studied. The aim of the present study was to investigate whether a KATP opener (diazoxide) and blocker (glibenclamide) modulates myocardial glycogen, lactate, and amino acid content before, during, and after ischemia. In isolated perfused rat hearts, we investigated the effect of diazoxide (30 microM) and glibenclamide (10 microM) administered 15 minutes before ischemia on myocardial glycogen, lactate, and amino acid content before, during, and after ischemia. Diazoxide increased left-ventricular developed pressure during reperfusion (P < 0.05) and decreased myocardial glycogen depletion (P < 0.05) and lactate accumulation (P < 0.05) during ischemia compared with the control group. Glibenclamide decreased myocardial glycogen content (P < 0.05) and increased myocardial lactate (P < 0.05) and alanine (P < 0.05) content before ischemia and reduced myocardial glycogen content after ischemia (P < 0.05) compared with control. KATP channel activation by diazoxide modulates myocardial metabolism. These findings suggest that activation of KATP channels protects against ischemia-reperfusion injury by a mechanism that involves decreased energy depletion.     

钙通道阻塞剂对大鼠肝细胞钙释放激活的钙电流的影响

目的 研究钙通道拮抗剂对大鼠肝细胞钙释放激活的钙电流（ＩＣＲＡＣ）的影响。方法 应用全细胞膜片箝技术。结果：ＩＣＲＡＣ的电流峰值是（－０．４１±０．０９）ｎＡ（ｎ＝１５）反转电位约为０ｍＶ。维拉帕米（Ｖｅｒ）地尔硫Ｚｕｏ（Ｄｉｌ）和硝苯地平（Ｎｉｆ）显著降低ＩＣＲＡＣ不影响它的反转电位,Ｖｅｒ５μｍｏｌ．Ｌ＾－１的抑制率是４０％±１２％（ｎ＝３）,Ｖｅｒ５０μｍｏｌ．Ｌ＾－１使ＩＣＲＡＣ的幅值从（     

Mechanisms of delayed preconditioning with A1 adenosine receptor activation in porcine coronary smooth muscle cells

This study examined the hypothesis that the activation of A1 adenosine receptor (A1AR) induces delayed cellular protection (DCP) in porcine coronary smooth muscle cells (PCSMC). The following groups of cultured PCSMC, subjected to simulated ischemia (SI) at 20 h were studied: (a) SI: with ischemia alone; (b) A1AR agonist chloro-N6-cyclopentyl adenosine (CCPA: CCPA (1 microM) alone; (c) CCPA + PKC inhibitor chelerythrine chloride (CCL): CCPA and 1 microM CCL; (d) CCPA + iNOS inhibitor S-methylthiourea (SMT): CCPA and 100 nM SMT; (e) CCPA + KATP channel blocker Glibenclamide (Glb): CCPA and 50 microM Glb; (f) CCPA + mitochondrial KATP channel blocker 5-hydroxydecanoate (5-HD): CCPA and 100 microM of 5-HD; (g) CCPA + A1AR antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX): CCPA and 1 microM DPCPX. The release of LDH into the medium as well as the amount of LDH remaining in the cells was used as a marker of cellular injury and cell viability. Up-regulation of A1AR, epsilon-PKC, iNOS and HSP 72i was detected through Westem blot analysis. The cellular resistance (%LDH remaining in the cells) acquired by PCSMC due to CCPA (59.42 +/- 1.57) was significantly blocked by CCL: 39.30 +/- 2.03; SMT: 41.37 +/- 1.98; Glb: 47.24 +/- 1.31; 5-HD: 47.69 +/- 1.40 and DPCPX: 42.92 +/- 0.79. CCPA increased the expression of A1AR (1.30 fold), epsilon-PKC (1.20 fold), iNOS (1.50 fold), and HSP 72i (1.70 fold) compared to the controls. CCPA-induced up-regulation of A1AR, epsilon-PKC, iNOS, HSP 72i, and the opening of both mitochondrial and sarcolemmal KATP channels may possibly participate in signaling cascade. Our study suggests that A1AR activation up-regulates iNOS, HSP 72i via epsilon-PKC signaling pathway to activate both mitochondrial and sarcolemmal KATP channels for cellular protection against SI in the cultured PCSMC.     

Cardioprotective effects of nicorandil in rabbits anaesthetized with halothane: potentiation of ischaemic preconditioning via KATP channels

1. The roles of ATP-sensitive K+ channels (KATP channels) in ischaemic or pharmacological preconditioning in the rabbit heart remain unclear. Infarct limitation by ischaemic preconditioning was abolished by the KATP channel blocker glibenclamide under ketamine/xylazine anaesthesia, but not under anaesthesia induced by pentobarbital. Infarct limitation by the KATP channel opener pinacidil was detected under ketamine/xylazine anaesthesia, but not under pentobarbital anaesthesia. Thus, these effects appear to be anaesthetic dependent. 2. In the present study, we examined whether nicorandil (a KATP channel opener nitrate) exhibits cardioprotective actions under halothane anaesthesia, another commonly used volatile anaesthetic. Control animals were subjected to 40 min coronary occlusion and 120 min reperfusion. Before 40 min ischaemia, the nicorandil group received nicorandil (100 microg/kg per min, i.v., for 10 min), the 5' preconditioning (PC) group received 5 min ischaemia/20 min reperfusion, the 2.5'PC group received 2.5 min preconditioning ischaemia/20 min reperfusion, the nicorandil +2.5'PC group received both nicorandil and 2.5 min ischaemia/20 min reperfusion, the nicorandil +2.5'PC + 5-hydroxydecanoate (5HD) group received both nicorandil and 2.5 min ischaemia/20 min reperfusion in the presence of 5-hydroxydecanoate (5HD; a KATP blocker) and the 5HD group received 5 mg/kg, i.v., 5HD alone. Myocardial infarct size in control (n = 7), nicorandil (n = 5), 5'PC (n = 8), 2.5'PC (n = 5), nicorandil + 2.5'PC (n = 5), nicorandil + 2.5'PC + 5HD (n = 5) and 5HD (n = 4) groups averaged 44.4 +/- 3.6, 41.7 +/- 5.7, 17.8 +/- 3.2,* 34.1 +/- 4.8, 21.3 +/- 4.2,* 39.1 +/- 5.6 and 38.9 +/- 5.0% of the area at risk, respectively (*P <0.05 vs control). 3. Thus, nicorandil alone did not have an infarct size-limiting effect in halothane-anaesthetized rabbits. However, the results suggest that even when nicorandil alone does not demonstrate a direct cardioprotective effect, it may enhance ischaemic preconditioning via KATP channels. Key words: ATP-sensitive K+ (KATP) channel, ischaemic preconditioning, myocardial infarction, nicorandil, rabbit.     

金属硫蛋白对大鼠硝酸甘油耐药性的影响(英文)

目的:评价金属硫蛋白(metallothionein, Met)在体内是否能改善硝酸甘油耐药的发生。方法:大鼠给予硝酸甘油(nitroglycerin, Nit)贴剂治疗两天(0.05 mg·h~(-1))以产生耐药。于耐药大鼠预先给予ZnCl_2以诱导内源性Met的合成及给予外源性Met15 mg·kg~(-1)·d~(-1)连续2 d。结果:Nit ZnCl_2组大鼠肝脏、血浆Met明显高于对照组(C组)。Nit组大鼠离体主动脉环的舒张反应最低。Nit ZnCl_2组大鼠及Nit Met组大鼠对SNP的降压反应明显强于Nit组。结论:外源性Met或内源性诱导合成的Met可以改善大鼠Nit耐药的发生。     

银杏提取物对过氧化氢损伤的培养大鼠心肌细胞的保护作用

探讨银杏叶提取物对过氧化氢损伤的培养心肌细胞的保护作用及其机制。方法；比色法测定乳酸脱氢酶活性；戊巴比妥酸法测定细胞内质质过氧化物含量；透射电镜下观察细胞超微结构。结果：过氧化氢导致心肌细胞ＬＤＨ释放从（２１６６±２４７）Ｕ．Ｌ＾－１增至（５１８０±６４８）Ｕ．Ｌ＾－１ＭＤＡ含量从每１０＾６细胞９３．５±０．２）ｎｍｏｌ增至（７．２±０．４）ｎｍｏｌ；．心肌细胞超微结构受到严重损伤。     

Mediation of the effect of nicotine on Kir6.1 channels by superoxide anion production

KATP channels are a complex of regulatory sulfonylurea receptor subunits and the pore-forming inward rectifiers such as Kir6.1. Using the whole-cell patch-clamp technique, we investigated the interaction of nicotine with the Kir6.1 subunit as well as the underlying mechanism. Stable expression of Kir6.1 in HEK-293 cells yielded a detectable inward rectifier KATP current. This inward current was significantly inhibited by PNU-37883A and by a specific anti-Kir6.1 antibody. Nicotine at 30 and 100 microM increased Kir6.1 currents by 42 +/- 11.8% and 26.2 +/- 14.6%, respectively (n = 4-6, P < 0.05). In contrast, nicotine at 1-3 mM inhibited Kir6.1 currents (P < 0.05). Nicotine at 100 microM increased the production of superoxide anion (O2) by 20.3 +/- 5.7%, whereas at 1 mM it significantly decreased the production of O2 by 37.7 +/- 4.3%. Coapplication of hypoxanthine (HX) and xanthine oxidase (XO) to the transfected HEK-293 cells resulted in a significant and reproducible increase in Kir6.1 currents (P < 0.05). The stimulatory effect of HX/XO on Kir6.1 current was abolished by tempol, a scavenger of O2. Tempol also abolished the stimulatory effect of 30 muM nicotine on Kir6.1 currents. In conclusion, nicotine stimulates Kir6.1 channel at least in part through the production of O2.     

钾通道抑制剂减弱吉非罗齐对离体大鼠胸主动脉环的舒张作用

目的观察吉非罗齐对大鼠离体胸主动脉肌源性反应的影响,并探讨其作用机制。方法采用离体血管张力方法观察吉非罗齐对SD大鼠胸主动脉环静息张力及苯肾上腺素(PE)预收缩的影响;观察一氧化氮合成酶(NOS)抑制剂、环氧合酶抑制剂和K+通道阻断剂对吉非罗齐作用的影响。结果吉非罗齐(1×10-5～3×10-4mol.L-1)对大鼠胸主动脉静息张力无影响,但对PE(10-6mol.L-1)所致的预收缩具有浓度依赖性舒张作用,其最大舒张率为最大舒张的80.42%±6.35%。电压依赖性钾通道(KV)阻断剂四氨基吡啶(4-AP,10-3mol.L-1)、钙激活钾通道(KCa)阻断剂四乙胺(TEA,10-2mol.L-1)、内向整流钾通道(KIR)阻断剂氯化钡(BaCl2,10-3mol.L-1)和ATP敏感钾通道(KATP)阻断剂格列苯脲(Gli,10-5mol.L-1)均可减弱吉非罗齐的血管舒张作用(P<0.05),而一氧化氮合酶(NOS)抑制剂L-NAME(10-4mol.L-1)及环氧酶抑制剂吲哚美辛(10-5mol.L-1)对吉非罗齐的舒张作用无影响(P>0.05)。结论吉非罗齐对大鼠主动脉具有舒张作用,该舒张作用与NO及前列环素无关;可能与开放KV、KCa、KIR和KATP通道有关。