低温暴露和恢复对棘胸蛙雌性亚成体生存力及能量物质消耗的影响

棘胸蛙(Paa spinosa)亚成体在人工驯养过程中容易出现越冬困难,非正常的冬眠可能会影响次年的繁育。以雌性棘胸蛙亚成体(1—2龄)为对象,研究该蛙在人工低温暴露(4℃保持90 d)条件下的生存力、机体能量物质消耗、肥满度、脏器系数的变化特征,以及这些参数在温度恢复至正常(由4℃缓慢升至22℃后保持7 d)后的变化情况。结果表明,该蛙在低温暴露过程中存活率逐渐降低,恢复期无死亡。肥满度(K)和体重/体长(Kwl)在低温暴露期间有逐渐升高的趋势,但两者在经历恢复期(22℃,7 d)后均恢复至初始水平(P>0.05)。胃系数和脾系数在低温暴露期呈明显的上升趋势(P<0.05),且两者在第90天均显著大于初始水平(P<0.05)。恢复期肝系数显著减小(P<0.05)。在低温暴露期各阶段肝脏和肌肉脂肪含量与初始无统计差异(P>0.05);肝脏水分在低温暴露期间呈明显下降趋势(P<0.05),而肌肉水分则与之相反;肝脏非脂肪干物质含量呈显著上升趋势(P<0.05),而肌肉非脂肪干物质则呈相反趋势。肝糖原含量随暴露时间的延长呈现显著上升趋势(P<0.05),低温暴露第60天和第90天肝糖原含量与初始相比分别增加59.4%和60.1%,而恢复期肝糖原含量则降至初始水平(P>0.05)。根据结果可以看出,在低温暴露过程中肝脏和肌肉脂肪含量变化不显著,同时肥满度、肝系数、肝脏非脂肪干物质和肝糖原含量均有不同程度的升高,而肌肉非脂肪干物质则显著减少(P<0.05),说明该蛙雌性亚成体在低温期主要消耗的能量物质不是脂肪而是肌肉非脂肪干物质,或者肌肉非脂肪干物质在组织间发生了大量转运。     

Cd~(2+),Zn~(2+)和Cu~(2+)对Physocypria kraepelini(介形纲)的急性毒性实验

采用急性毒性实验方法,研究了水环境中常见重金属离子Cd2+,Zn2+和Cu2+对介形类Physocypria kraepelini的急性毒性作用。实验过程按等差数间距设置6个Cd2+浓度梯度,按等比数间距设置9个Zn2+和9个Cu2+浓度梯度。结果表明:24、48、72和96h时Cd2+,Zn2+和Cu2+对P.kraepelini的半致死浓度(LC50)分别为1.37、0.39、0.21和0.04mg/l,217.27、34.36、23.77和8.42mg/l,及7.28、1.26、0.65和0.39mg/l。通过比较发现,P.kraepelini可以作为水体受Cd2+污染的判别生物;P.kraepelini对Cd2+,Zn2+和Cu2+的安全浓度分别为0.004、0.842和0.039mg/l,接近国家渔业水质标准(GB11607-89)规定的限值,因此其还可以作为渔业用水的判别生物。     

Pb~(2+)、Cr~(6+)、Hg~(2+)和Cu~(2+)对碱蓬幼苗生长及生理生化指标的影响

以水培法及分光光度法培养、测定碱蓬幼苗在重金属胁迫下的株高、鲜重及根数,叶绿素、可溶性蛋白和丙二醛含量等各项生长指标以及过氧化物酶、过氧化氢酶的活性变化.结果表明:Pb2+、Cr6+、Hg2+和Cu2+使碱蓬植株生长出现明显抑制效果的临界浓度分别为:45 mg/kg、15 mg/kg、10 mg/kg和5 mg/kg。此浓度胁迫下,碱蓬植株鲜重降低25%~30%、根数减少12%~34%。重金属处理后,碱蓬的叶绿素和可溶性蛋白含量下降、丙二醛含量上升,且处理与对照间差异显著。Pb2+、Cr6+、Hg2+、Cu2+处理的叶绿素总量分别是对照的61%、59%、55%和67%,可溶性蛋白含量分别是对照的66.7%、58.3%、41.7%和75%,而丙二醛含量分别是对照的167%、147%、114%和131%。4种重金属胁迫下的碱蓬植株体内过氧化物酶活性均高于对照,而过氧化氢酶活性低于对照。     

限食和再恢复投喂对鲮鱼生化组成的影响

在水温 19℃— 2 4℃条件下对鲮鱼 (初始体重 :88 86± 5 92g)进行了不同时间的限食处理后再充分投喂的恢复生长实验。结果表明 :限食状态下 ,肝脏糖原 ,肝脏脂肪和肌肉 (白肌 )糖原含量均显著降低 ;肝脏和肌肉水含量显著升高 :而肌肉脂肪 ,肝脏蛋白和肌肉蛋白变化都不显著 ;血糖 ,血脂和血浆蛋白含量都显著降低。再充分投喂后 ,各生化成分均恢复到对照组水平 ,表明鲮鱼在恢复生长过程中产生了显著的补偿效应     

镉致黑斑蛙肝脏氧化损伤与金属硫蛋白含量的变化

为观察镉对黑斑蛙(Rana nigromaculata)肝脏脂质过氧化产物和金属硫蛋白含量的影响,将黑斑蛙暴露于10.0mg·mL-1浓度的镉溶液中30d,分别测定了黑斑蛙在暴露4、10d和30d时肝脏组织中镉(Cd)、还原型谷胱甘肽(GSH)、金属硫蛋白(MT)和过氧化产物丙二醛(MDA)的含量。实验结果表明,黑斑蛙肝脏中镉的积累量、GSH和MT含量均随着镉暴露时间的延长而显著升高,具有明显的时间-效应关系;在镉暴露的第10天,肝MDA含量明显高于对照组。提示镉可对黑斑蛙肝脏造成氧化损伤,而GSH、MT含量的升高则可能是机体抗氧化损伤的机理之一。     

铜离子急性胁迫对虎纹蛙肝脏中三羧酸循环及自由基代谢的影响

为探明铜离子(Cu2+)对两栖动物肝脏线粒体中三羧酸(Tricarboxyl acid, TCA)循环及自由基代谢的毒理作用,采用静水暴露实验,研究了Cu2+不同浓度和不同暴露时间对虎纹蛙(Hoplobatrachus chinensis)肝脏线粒体中异柠檬酸脱氢酶(ICDHm)活性、-酮戊二酸脱氢酶(-KGDH)活性、抗超氧阴离子(anti-O2)活性、过氧化氢(H2O2)含量、抑制羟自由基(inhabit-OH)活性、一氧化氮(NO)含量以及一氧化氮合成酶(NOS)活性的影响。暴露实验共设置6个Cu2+浓度组(0.0、2.0、4.0、6.0、8.0和10.0 mg/L),分5个暴露时间(0、24h、48h、72h和96h)取材,对每个浓度的不同暴露时间分别取6个样本,测定TCA循环及自由基代谢的相关指标。结果显示,在TCA循环中随着Cu2+浓度的增加和暴露时间的延长,时间和浓度因素对ICDHm活性影响无显著性交互作用(P0.05),暴露时间的延长对ICDHm活性无显著性影响(P0.05),但随着Cu2+浓度的增加ICDHm活性逐渐减小;而时间和浓度因素对-KGDH活性影响有显著交互作用(P0.05),暴露处理后-KGDH活性下降,分别在24h和96h的4.0、6.0 mg/L时活性最低。在自由基代谢中,时间和浓度因素对抗O2活性、H2O2含量影响有显著交互作用(P0.05),而对抑制OH活性、NO含量、NOS活性的影响无显著性交互作用(P0.05)。不同时间随着Cu2+浓度的增加,抗O2活性均呈现出逐渐下降的趋势;实验处理后H2O2含量升高,在24h的6.0 mg/L时含量最大;随着暴露时间的延长和Cu2+浓度的增加抑制OH活性均逐渐降低;而NO含量和NOS活性的变化趋势基本相同,即随着Cu2+浓度的增加先增加后减少并趋近0浓度组,且都在6.0 mg/L时达到最大。研究结果表明急性Cu2+暴露对虎纹蛙肝脏线粒体中TCA循环及自由基代谢有显著的毒性作用。       

水相Cd2+在南美白对虾体内的富集及氧化应激特征

为阐明水相环境中重金属镉元素(Cadmium, Cd)在甲壳类海产品中的富集与代谢过程、亚细胞微区分布特征和生物体氧化应激效应, 文章以南美白对虾(Litopenaeus vannamei)为研究对象, 应用双箱动力学模型设置了水环境下不同Cd暴露水平的富集吸收与清水净化释放试验, 实时监测南美白对虾内脏团和肌肉组织的Cd含量及谷胱甘肽巯基转移酶(Glutathione S-transferase, GST)、谷胱甘肽过氧化物酶(Glutathione peroxidase, GPx)和过氧化氢酶(Catalase, CAT)酶活力随时间变化情况, 同时结合差速离心技术分析了Cd富集后在机体内脏组织团中的亚细胞微区分布特征。实验得出南美白对虾对水环境中Cd的富集能力与水体暴露浓度呈明显的正相关关系, 内脏团组织是南美白对虾最主要的Cd元素吸收与代谢组织, 其对Cd的吸收速率、净化速率、生物富集因子及平衡状态时Cd含量均显著高于肌肉组织, 在相同暴露剂量下前者的生物富集因子平均为后者的75.5倍, 肌肉组织的Cd生物学半衰期明显长于内脏组织; Cd主要储存于类金属硫蛋白(Metallothionein-like protein, MTLP)和细胞碎片(Cell debris, CD)组分中, 少部分存在于细胞器(Organelle, ORG)、富含金属颗粒(Metal-rich granules, MRG)和热敏感蛋白(Heat sensitive protein, HSP), 且随着富集过程的持续, Cd的亚细胞微区分布发生动态变化, MTLP、ORG和HSP中Cd含量百分比逐渐升高, CD和MRG中的Cd含量百分比呈逐渐下降; 在肝脏和肌肉组织中GST、GPx和CAT酶活力在Cd富集阶段均持续显著升高, 在净化释放阶段处于下降趋势, 同一试验组下肝脏组织中抗氧化酶酶活力明显高于对应的肌肉组织。研究旨在阐述甲壳类海洋生物对环境中Cd元素的富集与分布特征, 了解Cd富集可能性机理, 为海洋甲壳类Cd污染风险评价与环境控制提供科学依据。     

饥饿及再投喂对日本囊对虾糖代谢的影响

研究了日本囊对虾在饥饿和再投喂下血糖、肝胰脏糖原和肌糖原含量的变化.结果表明：在饥饿状态下,日本囊对虾肝胰脏糖原含量和血糖浓度在饥饿开始时迅速下降,肌糖原含量在饥饿10 d时下降到最低值,在饥饿10~15 d时通过糖原异生作用又恢复至最初水平,但随着饥饿时间的延长,糖原含量持续下降.恢复投喂后,肝胰脏糖原含量和肌糖原含量均能得到较好恢复,饥饿10 d和 15 d组的血糖浓度在恢复投喂10 d后显著高于对照组,但饥饿25 d组的血糖浓度始终显著低于对照.表明饥饿时间过长,对血糖浓度的恢复有较大影响     

Cd2+-B[α]P复合污染对菲律宾蛤仔急性毒性和解毒代谢酶活力的影响

文章研究了Cd2+-B[α]P复合污染对菲律宾蛤仔的急性毒性和鳃丝、消化盲囊解毒代谢酶活力的影响。结果表明:Cd2+对菲律宾蛤仔48、72、96h LC50分别为50.41、24.12、14.68 mg/L,Cd2+-B[α]P对菲律宾蛤仔的联合急性毒性48—96h表现为协同作用。Cd2+、B[α]P单一与复合污染对菲律宾蛤仔鳃丝、消化盲囊谷胱甘肽(GSH)含量、谷胱甘肽硫转移酶(GST)和超氧化物歧化酶(SOD)活力的影响显著(P<0.05),而对照组无显著变化。单一染毒组组织GSH含量在12d内呈峰值变化,分别于1d、3d达到最大值,12d后保持稳定,表现为恢复至对照组水平或被诱导;复合污染处理组组织GSH含量除Cd2++B[α]P(15μg/L+0.01μg/L)处理组在3d内呈峰值变化外,其他处理组均呈逐渐下降趋势,均于12d后稳定,被显著抑制。各染毒处理组组织GST、SOD活力在12d内呈峰值变化,分别于1d、3d达到最大值,12d后各处理组GST、SOD活力趋于稳定,GST活力与对照组无明显差异,而SOD活力明显高于对照组水平。由此可见,菲律宾蛤仔在Cd2+-B[α]P复合胁迫下急性毒性效应明显,组织解毒代谢酶活力表现出明显的时间、剂量效应性,鳃丝、消化盲囊GSH含量和SOD活力可作为菲律宾蛤仔Cd2+-B[α]P复合污染评价的潜在生物标志物。     

有氧运动对高脂饮食小鼠肝脏中CLK2蛋白表达的影响

目的: 探讨有氧运动对高脂饮食小鼠肝脏中Cdc2 激酶(CLK2)蛋白表达及肝脏脂肪含量的影响。方法: 雄性C57/BL6小鼠经正常饮食或高脂饮食16周后,分为正常饮食组、高脂饮食组和高脂饮食+运动组(8周有氧运动),每组10只小鼠。采用免疫印迹方法比较各组小鼠肝脏CLK2蛋白表达;采用油红O染色法比较各组小鼠肝脏脂肪含量;采用实时定量PCR方法比较各组小鼠脂肪代谢相关基因。结果:与正常饮食组小鼠相比,高脂饮食小鼠表现出胰岛素抵抗,肝脏CLK2蛋白含量增加,以及肝脏脂肪积累增加。然而有氧运动可改善高脂饮食小鼠胰岛素抵抗状态,并抑制肝脏中CLK2蛋白增加。结论:有氧运动可降低高脂饮食小鼠肝脏中CLK2蛋白表达,而改善肥胖小鼠肝脏脂肪堆积及代谢紊乱。     

Hormone-stimulated Mg(2+) accumulation into rat hepatocytes: a pathway for rapid Mg(2+) and Ca(2+) redistribution

Many diseases such as cardiac arrhythmia, diabetes, and chronic alcoholism are associated with a marked decrease of plasma and parenchymal Mg(2+), and Mg(2+) administration is routinely used therapeutically. This study uses isolated rat hepatocytes to ascertain if and under which conditions increases in extracellular Mg(2+) result in an increase in intracellular Mg(2+). In the absence of stimulation, changing extracellular Mg(2+) had no effect on total cellular Mg(2+) content. By contrast, carbachol or vasopressin administration promoted an accumulation of Mg(2+) that increased cellular Mg(2+) content by 13.2 and 11.8%, respectively, and stimulated Mg(2+) uptake was unaffected by the absence of extracellular Ca(2+). Mg(2+) efflux resulting from stimulation of alpha- or beta-adrenergic receptors operated with a Mg(2+):Ca(2+) exchange ratio of 1. These data indicate that cellular Mg(2+) uptake can occur rapidly and in large amounts, through a process distinct from Mg(2+) release, but operating only upon specific hormonal stimulation.     

大麦根细胞质膜Ca~(2+)-ATP酶和Ca~(2+)转运系统的特性

用大麦质膜微囊研究细胞质膜 Ca~(2+)转运过程,发现质膜 Ca~(2+)—ATP酶在反应系统中不存在Mg~(2+)时可正常表现活性。跨膜Ca~(2+)转运按其对Mg~(2+)的需求可分为两个过程,一个是不需Mg~(2+)的、具高Ca~(2+)亲和力和较低的转运能力;另一个则是需Mg~(2+)的、具低Ca~(2+)亲和力和较高的转运能力。前者的动力学特征与Ca~(2+)—ATP酶相近,而后者则相差很大。据此推测,大麦根细胞质膜上除Ca~(2+)—ATP酶外,还存在另一个不同的Ca~(2+)转运系统。由两者分别承担的Ca~(2+)转运过程在细胞钙信使系统中可能起着不同的作用。     

若干蝙蝠葛碱衍生物对人红细胞膜Ca~(2+)-Mg~(2+)-ATPase活力的影响

本文测定了数种蝙蝠葛碱衍生物对钙调素(CaM)激活的人红细胞膜Ca~(2+)-Mg~(2+)-ATPase活力的影响。结果表明,这些化合物对该酶都有不同程度的抑制作用,其机制表现为竞争性抑制,过量的CaM能完全逆转这些化合物所引起的抑制。当Ca~(2+)-Mg~(2+)-ATPase被胰蛋白酶(trypsin)限制性酶解完全活化后,其活力不再受CaM激活,但仍被这些化合物所抑制。     

跨膜Ca~(2+)梯度对肌质网Ca~3+-ATP酶调节的特异性

我们曾报道跨膜Ca~(2+)梯度可通过膜脂影响肌质网Ca~(2+)-ATP 酶的构象和活性。本文就跨膜Ca~(2+)梯度对肌质网Ca~(2+)-ATP 酶的调节是否具有特异性作进一步研究。结果表明这种特异性表现在两方面:一是跨膜Ca~(2+)梯度对肌质网Ca~(2+)-ATP 酶功能的调节不能归结于跨膜Ca~(2+)浓度梯度所导致的膜电位的作用,离子载体FCCP 可消除跨膜电位但并不影响肌质网Ca~(2+)-ATP 酶的活力;二是其它二价金属离子如Sr~(2+)的跨膜梯度对肌质网Ca~(2+)-ATP 酶活力基本无影响。荧光偏振系列探剂n-AS 测定的结果表明跨膜Ca~(2+)与Sr~(2+)梯度对嵌有Ca~(2+)-ATP 酶的脂酶体的中部流动性的影响有较大差异。而Ca~(2+)-ATP 酶的Ca~(2+)结合位点正处于脂双层中部,这进一步提示膜脂参与了跨膜Ca~(2+)梯度对Ca~(2+)-ATP 酶的调节作用。     

Mitochondria and Ca(2+) signaling

Mitochondria play a central role in cell homeostasis. Amongst others, one of the important functions of mitochondria is to integrate its metabolic response with one of the major signaling pathways - the Ca²⁺ signaling. Mitochondria are capable to sense the levels of cytosolic Ca²⁺ and generate mitochondrial Ca²⁺ responses. Specific mechanisms for both Ca²⁺ uptake and Ca²⁺ release exist in the mitochondrial membranes. In turn, the mitochondrial Ca²⁺ signals are able to produce changes in the mitochondrial function and metabolism, which provide the required level of functional integration. This essay reviews briefly the current available information regarding the mitochondrial Ca²⁺ transport systems and some of the functional consequences of mitochondrial Ca²⁺ uptake     

p-Nitrophenylphosphatase activity catalyzed by plasma membrane (Ca(2+) + Mg(2+)ATPase: correlation with structural changes modulated by glycerol and Ca(2+)

The plasma membrane (Ca²⁺+Mg²⁺)ATPase hydrolyzes pseudo-substrates such as p-nitrophenylphosphate. Except when calmodulin is present, Ca²⁺ ions inhibit the p-nitrophenylphosphatase activity. In this report it is shown that, in the presence of glycerol, Ca²⁺ strongly stimulates phosphatase activity in a dose-dependent manner. The glycerol- and Ca²⁺-induced increase in activity is correlated with modifications in the spectral center of mass (average emission wavenumber) of the intrinsic fluorescence of the enzyme. It is concluded that the synergistic effect of glycerol and Ca²⁺ is related to opposite long-term hydration effects on the substrate binding domain and the Ca²⁺ binding domain.     

Ca(2+) -independent vesicular catecholamine release in PC12 cells by nanomolar concentrations of Pb(2+)

Effects of Pb(2+) on vesicular catecholamine release in intact and ionomycin-permeabilized PC12 cells were investigated using carbon fibre microelectrode amperometry. Changes in intracellular Pb(2+) and Ca(2+) were measured from indo-1 fluorescence by confocal laser scanning microscopy. Depolarization of intact cells and superfusion of permeabilized cells with saline containing > or = 100 microm Ca(2+) rapidly evokes quantal catecholamine release. Superfusion with up to 10 microm Pb(2+) -containing saline evokes release of similar catecholamine quanta after a concentration-dependent delay. Thresholds to induce exocytosis within 30 min of exposure are between 1 and 10 microm Pb(2+) in intact cells and between 10 and 30 nm Pb(2+) in permeabilized cells. Additional inhibition of exocytosis occurs in permeabilized cells exposed to 10 microm Pb(2+). Using membrane-impermeable and -permeable chelators it is demonstrated that intracellular Ca(2+) is not required for Pb(2+) -induced exocytosis. In indo- 1-loaded cells Pb(2+) reduces the fluorescence intensity after a concentration-dependent delay, whereas the fluorescence ratio, indicating intracellular Ca(2+) concentration, remains unchanged. The delay to detect an increase in free intracellular Pb(2+) (> or = 30 nm) is much longer than the delay to Pb(2+) -induced exocytosis, indicating that cytoplasmic components buffer Pb(2+) with high affinity. It is concluded that Pb(2+) acts as a high-affinity substitute for Ca(2+) to trigger essential steps leading to vesicular catecholamine release, which occurs when only approximately 20% of the intracellular high-affinity binding capacity ( approximately 2 attomol/cell) is saturated with Pb(2+).     

'Ca(2+)-induced Ca(2+) entry' or how the L-type Ca(2+) channel remodels its own signalling pathway in cardiac cells

The adjustment of Ca²⁺ entry in cardiac cells is critical to the generation of the force necessary for the myocardium to meet the physiological needs of the body. In this review, we present the concept that Ca²⁺ can promote its own entry through Ca²⁺ channels by different mechanisms. We refer to it under the general term of ‘Ca²⁺-induced Ca²⁺ entry’ (CICE). We review short-term mechanisms (usually termed facilitation) that involve a stimulating effect of Ca²⁺ on the L-type Ca²⁺ current (I_Ca-L) amplitude (positive staircase) or a lessening of Ca²⁺-dependent inactivation of I_Ca-L. This latter effect is related to the amount of Ca²⁺ released by ryanodine receptors (RyR2) of the sarcoplasmic reticulum (SR). Both effects are involved in the control of action potential (AP) duration. We also describe a long-term mechanism based on Ca²⁺-dependent down-regulation of the Kv4.2 gene controlling functional expression of the repolarizing transient outward K⁺ current (I_to) and, thereby, AP duration. This mechanism, which might occur very early during the onset of hypertrophy, enhances Ca²⁺ entry by maintaining Ca²⁺ channel activation during prolonged AP. Both Ca²⁺-dependent facilitation and Ca²⁺-dependent down-regulation of I_to expression favour AP prolongation and, thereby, promote sustained voltage-gated Ca²⁺ entry used to enhance excitation–contraction (EC) coupling (with no change in the density of Ca²⁺ channels per se). These self-maintaining mechanisms of Ca²⁺ entry have significant functions in remodelling Ca²⁺ signalling during the cardiac AP. They might support a prominent role of Ca²⁺ channels in the establishment and progression of abnormal Ca²⁺ signalling during cardiac hypertrophy and congestive heart failure.     

Mobilizing store Ca(2+) in the presence of La(3+) evokes exocytosis in bovine chromaffin cells

The effect on exocytosis of La(3+), a known inhibitor of plasma membrane Ca(2+)-ATPases and Na(+)/Ca(2+) exchangers, was studied using cultured bovine adrenal chromaffin cells. At high concentrations (0.3-3 mM), La(3+) substantially increased histamine-induced catecholamine secretion. This action was mimicked by other lanthanide ions (Nd(3+), Eu(3+), Gd(3+), and Tb(3+)), but not several divalent cations. In the presence of La(3+), the secretory response to histamine became independent of extracellular Ca(2+). La(3+) enhanced secretion evoked by other agents that mobilize intracellular Ca(2+) stores (angiotensin II, bradykinin, caffeine, and thapsigargin), but not that due to passive depolarization with 20 mM K(+). La(3+) still enhanced histamine-induced secretion in the presence of the nonselective inhibitors of Ca(2+)-permeant channels SKF96365 and Cd(2+), but the enhancement was abolished by prior depletion of intracellular Ca(2+) stores with thapsigargin. La(3+) inhibited (45)Ca(2+) efflux from preloaded chromaffin cells in the presence or absence of Na(+). It also enhanced and prolonged the rise in cytosolic [Ca(2+)] measured with fura-2 during mobilization of intracellular Ca(2+) stores with histamine in Ca(2+)-free buffer. The results suggest that the efficacy of intracellular Ca(2+) stores in evoking exocytosis is enhanced dramatically by inhibiting Ca(2+) efflux from the cell.     

Effects of chronic hypoxia on Ca(2+) stores and capacitative Ca(2+) entry in human neuroblastoma (SH-SY5Y) cells.

Microfluorimetric measurements of intracellular calcium ion concentration [Ca(2+)](i) were employed to examine the effects of chronic hypoxia (2.5% O(2), 24 h) on Ca(2+) stores and capacitative Ca(2+) entry in human neuroblastoma (SH-SY5Y) cells. Activation of muscarinic receptors evoked rises in [Ca(2+)](i) which were enhanced in chronically hypoxic cells. Transient rises of [Ca(2+)](i) evoked in Ca(2+)-free solutions were greater and decayed more slowly following exposure to chronic hypoxia. In control cells, these transient rises of [Ca(2+)](i) were also enhanced and slowed by removal of external Na(+), whereas the same manoeuvre did not affect responses in chronically hypoxic cells. Capacitative Ca(2+) entry, observed when re-applying Ca(2+) following depletion of intracellular stores, was suppressed in chronically hypoxic cells. Western blots revealed that presenilin-1 levels were unaffected by chronic hypoxia. Exposure of cells to amyloid beta peptide (1-40) also increased transient [Ca(2+)](i) rises, but did not mimic any other effects of chronic hypoxia. Our results indicate that chronic hypoxia causes increased filling of intracellular Ca(2+) stores, suppressed expression or activity of Na(+)/Ca(2+) exchange and reduced capacitative Ca(2+) entry. These effects are not attributable to increased amyloid beta peptide or presenilin-1 levels, but are likely to be important in adaptive cellular remodelling in response to prolonged hypoxic or ischemic episodes.