GDP对柴胡皂甙(Ⅰ)促大鼠胰腺腺泡酶分泌和升高[Ca~(2 )]_i的影响

目的:研究鸟苷二磷酸(GDP)对柴胡皂甙(Ⅰ)[SA(Ⅰ)]刺激大鼠胰腺腺泡酶分泌和胞内钙离子升高的影响。方法:分离大鼠胰腺腺泡细胞,用链球菌溶血素-O(SLO)通透细胞膜,检测腺泡分泌蛋白量标志腺泡酶分泌功能。用钙离子荧光指示剂Fluo-3和荧光光谱测定胞内钙离子浓度。结果:GDP可抑制SA(Ⅰ)促胰腺腺泡的酶分泌作用,抑制作用随剂量增加而加强;SA(Ⅰ)10μmol/L以双峰值为特征使[Ca~(2 )]_i显著上升;GDP5mmol/L,导致[Ca~(2 )]_i逐步升高且两个峰值消失。细胞通透以后,与正常细胞相比,SA(Ⅰ)刺激的30min酶分泌的累积量下降了57％;GDP5mmol/L使SA(Ⅰ)刺激的早期酶分泌速率进一步降低。结论:GDP通过抑制细胞[Ca~(2 )]_i的升高抑制了SA(Ⅰ)刺激的胰腺腺泡酶分泌作用。     

高糖对原代培养血管内皮细胞[Ca^2＋]i和分泌LN和IV—C的影响

目的：旨在探讨体外培养条件下糖状态对血管内皮细胞的影响。方法：以原代培养人脐带静脉内皮细胞为材料，用Fura-2荧光检测法观察高糖对原代培养血管内皮细胞内钙离子浓度([Ca^2 ]i）的影响，用放射免疫分析法观察高糖作用下血管内皮细胞分泌基底膜蛋白成分Ⅳ型胶原蛋白（IV－C）和层粘连蛋白（LN）的情况。结果：在11．11mmol/L、16.67mmol/L和33.33mmol/L糖浓度下培养24小时，血管内皮细胞[Ca^2 ]i分别升高了1．74、2．84和6．74倍。发现不同糖浓度作用下血管内皮细胞分泌IV－C的量均无变化；在16．67mmol/L糖浓度下培养24小时血管内皮细胞分泌LN的量下降了26．69％。结论：在较短时间内糖浓度升高可引起血管内皮细胞[Ca^2 ]i升高，而对血管内皮细胞分泌LN起抑制作用，对IV－C的分泌无明显影响。在糖尿病微血管病变早期，高糖可能通过血管内皮细胞[Ca^2 ]i升高而起主要作用。     

龙葵碱对HepG2细胞线粒体膜电位及细胞内[Ca^2＋]i的影响

目的：观察龙葵碱对HepG2细胞线粒体膜电位及细胞内[Ca^2＋]i的影响，揭示龙葵碱诱导细胞凋亡的机制。方法：采用AO／EB双染HepG2细胞，激光共聚焦扫描显微镜观察细胞形态学改变；TMRE单染HepG2细胞，激光共聚焦扫描显微镜观察细胞线粒体膜电位的改变；Fluo-3／AM单染HepG2细胞，激光共聚焦扫描显微镜观察细胞内[Ca^2＋]i的改变；TMRE和Fluo-3／AM双染HepG2细胞，激光共聚焦扫描显微镜同时观察细胞线粒体膜电位和细胞内[Ca^2＋]i的改变。结果：形态学实验表明0．0032μg／mL、0．016μg／mL龙葵碱使细胞外周呈微弱皱缩状改变，0．08、0．4、2μg／mL龙葵碱使HepG2细胞出现大量碎片及凋亡小体等典型的细胞凋亡形态，即龙葵碱能够诱导HepG2细胞凋亡；TMRE单染激光共聚焦测定表明龙葵碱能够降低HepG2细胞膜电位；Fluo-3／AM单染激光共聚焦测定表明龙葵碱能够升高肿瘤细胞内[Ca^2＋]。浓度；TMRE和Fluo-3／AM双染激光共聚焦观察表明龙葵碱在降低线粒体膜电位的同时能够升高细胞内[Ca^2＋]i浓度。结论：龙葵碱能够诱导HepG2细胞凋亡，其机制为降低HepG2细胞膜电位，开放细胞膜PT通道，使细胞内Ca^2＋顺浓度梯度转运，从而升高细胞内Ca^2＋浓度启动细胞凋亡机制。     

钙流拮抗药对眼镜蛇心脏毒升高大鼠心肌胞浆Ca~（2＋）作用的影响

Ｆｕｒａ－２荧光测定实验显示，眼镜蛇心脏毒（ＣＴＸ）能明显升高新鲜分离的大鼠心肌细胞的胞浆Ｃａ２＋浓度。维拉帕米在完全阻断高Ｋ＋引起胞浆Ｃａ２＋升高的浓度下（１μｍｏｌ·Ｌ－１）．能明显抑制ＣＴＸ作用，但不能阻断之。１．５μｍｏｌ·Ｌ－１ＣＴＸ使离体大鼠Ｌａｎｇｅｎｄｏｒｆｆ心脏收缩幅度逐渐减少，最后心脏停搏于收缩期。维拉帕米及硝苯吡啶均能明显延长心脏的搏动时间，但不能阻止ＣＴＸ引起的心脏停搏。结果提示，ＣＴＸ引起膜去极化使电位依赖性Ｃａ２＋通道开放不是ＣＴＸ触发Ｃａ２＋内流的唯一机理。     

维拉帕米对大鼠脑突触体内Ca^2＋和Ca^（2＋）Mg^（2＋）—ATP酶的影响

维拉帕米１０，５０和１００μｍｏｌ．Ｌ＾－１能增加高Ｋ＾＋和去甲肾上腺素所致大鼠脑突触体内激离Ｃａ＾２＋的浓度，但使静息状态突触体内游离Ｃａ＾２＋浓度下降。Ｖｅｒ还抑制突触体Ｃａ＾（２＋）Ｍｇ＾（２＋）－ＡＴＰ酶活性。结果提示：与静息状态不同，在神经末梢受到刺激时，Ｖｅｒ可能是通过抑制ＣａＭ，进而抑制Ｃａ＾（２＋）Ｍｇ＾（２＋）－ＡＴＰ酶活性，使胞浆内游离Ｃａ＾（２＋）升高，引起递质释放量增加。     

苄普地尔降低左甲状腺素诱发升高的大鼠脑线粒体钙~（2＋）镁~（2＋）－ATP酶活力

苄普地尔降低左甲状腺素诱发升高的大鼠脑线粒体钙２＋镁２＋ＡＴＰ酶活力陈丁丁，戴德哉，储永新（中国药科大学药理研究室，南京２１０００９，中国）关键词钙通道阻滞剂；苄普地尔；普萘洛尔；左甲状腺素；大脑；线粒体；钙２＋镁２＋ＡＴＰ酶目的：研究苄普地尔是...     

西洋参茎叶皂甙单体P－F_（11）对培养大鼠心肌细胞动作电位的作用

从西洋参茎叶皂甙中分离提取的Ｐｓｅｕｄｏｇｉｎｓｅｎｏｓｉｄｅ－Ｆ１１（３、１０、３０ｍｇ·Ｌ－１，Ｐ－Ｆ１１）使培养的Ｗｉｓｔａｒ大鼠心肌细胞动作电位的幅值、动作电位时程、阈电位、最大舒张电位、０期最大除极速率和复极１０％、５０％水平的动作电位时程剂量依赖性增大。Ｐ－Ｆ１１（１０ｍｇ·Ｌ－１）的作用可被维拉帕米（２μｍｏｌ·Ｌ－１）所对抗，Ｐ－Ｆ１１（３０ｍｇ·Ｌ－１）与ＢａｙＫ８６４４（０．７５ｍｍｏｌ·Ｌ－１）比较对心肌细胞动作电位的电参数的作用相似。实验结果表明，Ｐ－Ｆ１１可能具有钙通道激活作用。     

Vasopressin-evoked [Ca2+]i responses in neonatal rat cardiomyocytes.

The presence of arginine vasopressin (AVP) V1 receptors on neonatal rat cardiomyocytes (NRCs) linked to processes capable of elevating intracellular free calcium ([Ca2+]i) is now firmly established. This study examined the sources and signaling involved in [Ca2+]i elevations evoked by AVP in NRCs. AVP promoted increases in both [Ca2+]i and 1,4,5-inositoltrisphosphate (IP3) levels in NRCs. The degree of [Ca2+]i elevation was less than that of angiotensin II, but greater than that of endothelin-1. Extracellular Mg2+ depletion led to diminution of the maximal [Ca2+]i response, with a rightward shift in the concentration-response curves to AVP. The phospholipase C inhibitors, D-609, NCDC, or U73122, and the IP3 receptor blocker, heparin, abolished the [Ca2+]i response to AVP. Neither cyclooxygenase inhibition with indomethacin nor PKC inhibition with staurosporine had any effect. Neither ryanodine nor caffeine, which deplete sarcoplasmic reticulum (SR) Ca2+ stores, nor ruthenium red, which inhibits both SR and mitochondrial Ca2+ stores, affected [Ca2+]i responses to AVP. The SR Ca2+ pump inhibitor, cyclopiazonic acid, abolished, and removal of extracellular Ca2+ attenuated, the response to AVP. These data indicate that activation of cardiac V1 receptors by AVP results in mobilization of Ca2+ from a distinct, non-SR, nonmitochondrial, intracellular Ca2+ pool that is Ca2+ pump replenished and IP3 sensitive. This process occurs secondary to phospholipase C (PLC)-mediated generation of IP3, requires the presence of Mg2+ and extracellular Ca2+, and occurs in a manner independent of PKC and cyclooxygenase activation. Such mechanisms of Ca2+ mobilization might indicate a distinct role for AVP in cardiac physiology and disease.     

Effects of tolbutamide and N-benzoyl-D-phenylalanine (NBDP) on the regulation of [Ca2+]i oscillations in mouse pancreatic islets.

The sulfonylurea derivative, tolbutamide, and the phenylalanine derivative, N-benzoyl-D-phenylalanine (NBDP), both of which stimulate insulin secretion through interaction with the sulfonylurea receptor (SUR1), were studied for their ability to increase the [Ca(2+)](i) and to interact with the glucose-induced slow large amplitude [Ca(2+)](i) oscillations in isolated mouse pancreatic islets. Tolbutamide as well as NBDP induced [Ca(2+)](i) oscillations of extremely slow frequency. Both compounds also lowered the threshold for the glucose-induced slow large amplitude [Ca(2+)](i) oscillations and significantly reduced their frequency in intact islets as well as in single pancreatic beta cells. These [Ca(2+)](i) oscillations apparently require a glucokinase-mediated glycolytic flux. This conclusion is supported by the observations that KIC, a mitochondrial fuel, cannot replace glucose in this synergism and that mannoheptulose, an inhibitor of glucokinase and glucose-induced insulin secretion, abolishes these slow [Ca(2+)](i) oscillations. In conclusion, these compounds potentiate the effect of glucose. This additive effect is the likely result of a synergistic closing action upon the ATP-sensitive K(+) (K(ATP)) channel, mediated in the case of glucose through an action upon the channel protein itself of ATP generated in glucose catabolism and in the case of tolbutamide and NBDP upon the sulfonylurea receptor (SUR1) associated with this channel.     

Group 1 mGlu receptors elevate [Ca2+]i in rat cultured cortical type 2 astrocytes: [Ca2+]i synergy with adenosine A1 receptors.

Brain macroglia are known to express a diverse array of neurotransmitter receptors whose signal transduction pathways may be subject to heteroreceptor 'cross-talk'. In the current study we have examined group 1 mGlu receptor-evoked [Ca2+]i signalling, and possible heteroreceptor cross-talk, in cultured type 2 astrocytes. The selective group 1 metabotropic glutamate (mGlu) receptor agonist (S)-3,5-dihydroxyphenylglycine (DHPG) elevated [Ca2+]i (EC50 = 1.7 +/- 0.6 microM); an effect reversed by the selective mGlu receptor antagonist (S)-alpha-methyl-4-carboxyphenylglycine (IC50 = 52.7 +/- 8.7 microM). DHPG-evoked [Ca2+]i responses were abolished by (1) thapsigargin (100 nM), implicating the involvement of internal Ca2+ stores in group 1 mGlu [Ca2+]i responses and (2) the removal of extracellular Ca2+. When applied alone, the selective adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA, 100 nM) failed to influence [Ca2+]i. However, in the presence of 1 microM DHPG, CPA potently (EC50 = 12.3 +/- 1.9 nM) increased [Ca2+]i responses. In the presence of 100 nM CPA, the efficacy of DHPG was doubled without any significant change in the DHPG EC50 value. This effect was reversed by either the selective adenosine A1 receptor antagonist, 8-cyclopentyltheophylline (IC50 = 50.3 +/- 19.9 nM) or overnight incubation with Pertussis toxin (100 ng/ml). We conclude that (1) type 2 astrocytes contain group 1 mGlu receptors coupled to [Ca2+]i signalling and (2) co-activation of adenosine A1 receptors enhances group 1 mGlu-evoked [Ca2+]i responses in these cells via a Gi/o G protein-mediated mechanism.     

Effect of APGW-amide on [Ca2+]i in rat pheochromocytoma PC12 cells

In order to determine whether Ala-Pro-Gly-Try-NH2 (APGW-amide) could affect mammalian excitable cells, we investigated the effect of APGW-amide in PC12 cells. APGW-amide caused a rapid [Ca2+]i elevation, which was completely prevented by elimination of extracellular Ca2+ with EGTA and inhibited by two L-type Ca2+ channel blockers. [Ca2+]i elevation was also blocked by a specific PKC inhibitor and prolonged pretreatment of cells with PMA. These results indicate that APGW-amide elevates [Ca2+]i in PC12 cells, possibly by Ca2+ influx via L-type Ca2+ channel activated by PKC.     

甲状旁腺素对大鼠心肌细胞内游离钙和细胞凋亡的影响

目的　研究甲状旁腺素 (PTH)对心肌细胞内游离钙以及细胞肥大和凋亡的影响。方法　利用培养的新生大鼠心肌细胞 ,以Fluo 3/AM负载 ,通过激光共聚焦显微镜(LSCM)测定细胞内游离钙浓度 ([Ca2 + ] i) ;以细胞面积和细胞蛋白含量作为心肌细胞肥大指标 ;采用电镜和流式细胞术观察细胞凋亡的变化。结果　PTH1～ 34 0 0 1和 0 1 μmol·L- 1 刺激 7d后 ,心肌细胞内钙荧光强度以及心肌细胞面积和蛋白含量、细胞凋亡率较对照组显著增加。而 0 1 μmol·L- 1 PTH1～ 34 刺激的同时分别加入 1、1 0 μmol·L- 1 硝苯地平 ,上述指标改善 ,但未能达正常。结论　PTH1～ 34 可显著增加心肌细胞 [Ca2 + ] i,诱导细胞肥大和凋亡 ,并呈浓度依赖性 ,电压依赖性钙通道开放引起的细胞外钙内流增加为其机制之一     

Comparison of the effects of caffeine and other methylxanthines on [Ca2+]i in rat ventricular myocytes.

1. The effects of caffeine and other methylxanthines were investigated on intracellular calcium concentration ([Ca2+]i) and contraction in rat isolated ventricular myocytes. The use of the fluorescent indicator, Indo-1, allowed simultaneous measurement of [Ca2+]i and the intracellular concentration of the methylxanthines. 2. Rapid application of caffeine (10 mM) produced a transient rise of [Ca2+]i which decayed to resting levels. This was accompanied by a transient contraction which decayed to a level above baseline. The addition of theophylline also produced a transient increase of [Ca2+]i. However, following the initial transient, contraction decayed before redeveloping to a maintained level. 3. Direct measurements showed that [caffeine]i rose more quickly than did [theophylline]i. The slower rise of [theophylline]i was associated with a delay in the increase of [Ca2+]i. At lower concentrations of the methylxanthines, theophylline was less effective than caffeine at initiating Ca release. The rate of entry of theobromine was similar to that of theophylline. 4. Isocaffeine did not produce a rise of [Ca2+]i. The rate of rise of [isocaffeine]i was much slower than that of either caffeine or theophylline. 5. Measurements of the oil:water partition coefficient showed that the order of relative partitioning into oil was: caffeine > theophylline > theobromine > isocaffeine. This is similar to the order of rate of entry into the cell. 6. We conclude that many of the differences in the effects of these methylxanthines can be attributed to differences in membrane permeability due to differences in oil:water partition.     

Effect of Ca2+ antagonists on high-K+ evoked increase in [Ca2+]i in rat cerebral synaptosomes and hippocampal neurons.

By fura-2 fluorometry, we investigated the direct effects of Ca2+ antagonists including a new benzothiazepine, clentiazem, on the high-K(+)-evoked increase in the concentration of cytosolic free Ca2+ ([Ca2+]i) in rat cerebral synaptosomes and cultured hippocampal neurons. In both preparations, metal ions inhibited the high-K(+)-induced increase in [Ca2+]i, in the following order: La3+ greater than Cd2+ much greater than Ni2+. Although flunarizine and nicardipine inhibited the K(+)-induced increase in [Ca2+]i in synaptosomes, other Ca2+ antagonists, including clentiazem and nitrendipine, had little effect at 10 microM. In hippocampal neurons, clentiazem inhibited the K(+)-induced increase in [Ca2+]i at 10 microM, as did flunarizine and nicardipine. However, nifedipine and nitrendipine had little effect in either cultured neurons or in synaptosomes.     

Effects of ovariectomy and 17 beta-oestradiol replacement on [Ca2+]i in female rat cardiac myocytes

1. The present study investigated the effects of ovariectomy (OVX) and 17beta-oestradiol replacement on [Ca2+]i in rat freshly isolated cardiac myocytes. 2. Myocytes were isolated from the hearts of sham, OVX and OVX + 17beta-oestradiol-replaced female rats by enzymatic digestion with collagenase. Changes in [Ca2+]i in response to varied extracellular [Ca2+] were measured using the Ca2+-sensitive dye fura-2, with the contractile responses of each cell measured as cell shortening. 3. Increasing extracellular [Ca2+] resulted in increased [Ca2+]i in all three groups. Peak [Ca2+]i and the amplitude of the Ca2+ transient were significantly greater (P < 0.01) in cells from OVX animals compared with cells from both sham and 17beta-oestradiol-replaced OVX animals. 4. The time-course of decay of the Ca2+ transient was significantly faster (P < 0.02) in OVX cells compared with both sham and 17beta-oestradiol-replaced cells. In addition, time to 50% relaxation was significantly faster (P < 0.04) and extent of shortening significantly greater (P < 0.01) in OVX cells than in either sham or 17beta-oestradiol cells. 5. These data demonstrate clear differences in peak [Ca2+]i and the amplitude of the Ca2+ transient between OVX female rat cardiac myocytes compared with intact and 17beta-oestradiol-replaced OVX female rat cardiac myocytes. This suggests that oestrogen may play a long-term role in limiting Ca2+ entry into the cardiac myocyte.     

The effects of GABAB receptor agonists and antagonists on potassium-stimulated [Ca2+]i in rat brain synaptosomes

The effects of GABAB agonists and putative antagonists on intrasynaptosomal calcium ion concentrations ([Ca2+]i) after stimulation with potassium ions were studied with the fluorescent probe Quin 2. gamma-Aminobutyric acid and (-)-baclofen, but not (+)-baclofen, produced a dose-dependent inhibition of the potassium-stimulated [Ca2+]i in cortical synaptosomes from the rat. This effect was mimicked by another GABAB agonist SL75102 and weakly by muscimol. It was not inhibited by the alpha-adrenoceptor antagonist phentolamine. This system thus appears to provide a useful test of GABAB receptor function. None of the putative GABAB antagonists, phaclofen, delta-aminovaleric acid or beta-phenyl GABA inhibited responses to (-)-baclofen. Indeed, all three compounds produced similar responses to that seen with (-)-baclofen, suggesting that they act as agonists in this system. These data suggest that those GABAB receptors modulating [Ca2+]i have a distinct pharmacology from post-synaptic GABAB receptors, defined in electrophysiological experiments.