牛磺酸对血管紧张素Ⅱ改变培养心肌细胞内游离Ca2+浓度作用的影响

目的和方法 :用Fura 2 /AM .荧光显示测定细胞内游离Ca2 浓度 ([Ca2 ]i)的方法 ,我们研究了牛磺酸 (Tau)对血管紧张素Ⅱ (AngⅡ )引起的培养心肌细胞 [Ca2 ]i变化的影响。结果 :在有Ca2 和无Ca2 的缓冲液中 ,AngⅡ (1 ,1 0 ,1 0 0 ,1 0 0 0nmol/L)能浓度依赖性地引起 [Ca2 ]i升高。在含Ca2 的缓冲液中 ,Tau(1 0 ,2 0mol/L)可依浓度地抑制AngⅡ (1 0 0nmol/L)引起的 [Ca2 ]i升高 ;但在无Ca2 的缓冲液中 ,牛磺酸无此作用。用ryanodine(Rya ,1 μmol/L)预先耗竭细胞内贮存的Ca2 后 ,AngⅡ (1 0 0nmol/L)仍能引起 [Ca2 ]i进一步升高 :AngⅡ的这一作用能被Tau(2 0mmol/L)显著抑制。结论 :在培养的乳鼠心肌细胞 ,Tau能够通过抑制AngⅡ引起的Ca2 内流而拮抗AngⅡ升高 [Ca2 ]i的作用。     

胍丁胺对大鼠心室肌细胞内游离钙浓度的影响

本研究旨在观察胍丁胺 (agmatine ,Agm)对分离大鼠心室肌细胞内游离钙浓度 ( [Ca2 +]i)的影响。用酶解方法分离大鼠心室肌细胞 ,用Fluo 3 AM负载 ,然后用激光共聚焦法测定单个心室肌细胞 [Ca2 +]i 的荧光强度 (fluorescenceintensity ,FI) ,结果以FI或相对荧光强度 (F/F0 % )表示。实验结果表明 ,在正常台氏液 (含钙 1 0mmol/L)和无钙台氏液中 ,单个大鼠心室肌细胞的荧光密度分别为 12 8 8± 13 8和 119 6± 13 6,两者无差异。Agm 0 1、1和 10mmol/L浓度依赖性地显著降低细胞的钙浓度 ;在正常台氏液中加入EGTA 3mmol/L ,Agm同样降低细胞的钙浓度。KCl 60mmol/L ,PE 3 0 μmol/L ,和Bay K 864 410 μmol/L均升高心室肌细胞的[Ca2 +]i。Agm同样降低高浓度KCl、Bay K 864 4和PE诱发的心室肌细胞 [Ca2 +]i 升高。当细胞外液钙浓度由 1mmol/L增加到 10mmol/L时 ,诱发心室肌细胞钙超载 ,同时部分心室肌细胞产生可传播的钙波 (Ca2 +wave) ,Agm 1mmol/L降低钙波的传播速度和持续时间 ,最终阻断钙波。以上结果提示 ,Agm对心室肌细胞的胞浆[Ca2 +]i具有抑制作用 ,此作用通过阻断电压依赖性钙通道而实现 ;并可能与抑制大鼠心室肌细胞内钙释放有关     

白藜芦醇降低大鼠心室肌细胞内游离钙浓度

实验旨在研究白藜芦醇(resveratrol)对大鼠心室肌细胞内钙浓度(intracellular calcium concentratoin,[Ca2+]i)的影响.应用激光共聚焦显微镜技术记录心室肌细胞内的钙荧光强度.结果表明在正常台氏液和无钙台氏液中,白藜芦醇(15～60μmol/L)呈浓度依赖性地降低[Ca2+]i.蛋白酪氨酸磷酸酶抑制剂正钒酸钠(sodium orthovanadate,1.0 mmol/L)和L型Ca2+通道激动剂Bay K8644(10 μmol/L)可部分抑制正常台氏液中白藜芦醇的效应.但NO合酶阻断剂L-NAME(1.0 mmol/L)对白藜芦醇的作用无影响.白藜芦醇也能明显抑制无钙台氏液中由低浓度ryanodine(1.0 nmol/L)引起的[Ca2+]i增加.当细胞外液钙浓度由1 mmol/L增加到10 mmol/L而诱发心室肌细胞钙超载时,部分心室肌细胞产生可传播的钙波,白藜芦醇(60 μmol/L)可降低钙波的传播速度和持续时间,最终阻断钙波.结果提示,白藜芦醇能够降低心室肌细胞内游离钙浓度,此作用可能与其抑制电压依赖性Ca2+通道、酩氨酸激酶和肌浆网内钙释放有关.     

大鼠结肠平滑肌细胞的钙库操纵性通道

目的:探讨大鼠结肠平滑肌细胞是否存在钙库操纵性通道(SOC)。方法:荧光探针Fura-2/AM标记细胞内游离Ca2+后,用荧光分光光度计检测毒胡萝卜素(thapsigargin)和咖啡因(caffeine)耗竭胞内钙库后激活的SOC通道对酶解分离的大鼠结肠平滑肌细胞[Ca2+]i的影响。结果:在无Ca2+缓冲液中,thapsigargin(1μmol/L)以及caf-feine(10 mmol/L)分别使[Ca2+]i由静息时(68.32±3.43)nmol/L升高至(240.85±12.65)nmol/L(、481.25±34.77)nmol/L,继之,向细胞外液中引入两种浓度的Ca2+(1.5 mmol/L和3.0 mmol/L),导致[Ca2+]i进一步升高,分别为(457.55±19.80)nmol/L、(1005.93±54.62)nmol/L;(643.88±34.65)nmol/L、(920.16±43.25)nmol/L。且上述升高效应对维拉帕米(verapamil,5μmol/L)以及KCl引起的细胞膜去极化不敏感,但可被La3+(1 mmol/L)抑制。结论:在酶解分离的大鼠结肠平滑肌细胞上,存在胞内钙库耗竭激活的SOC通道,为支持在电兴奋性细胞上存在库容性Ca2+内流提供了实验和理论依据。     

八肽胆囊收缩素激活钙离子通道和酪氨酸激酶诱导豚鼠心肌细胞内的游离钙增高

探讨八肽胆囊收缩素(CCK-8)对豚鼠单个心肌细胞内游离钙浓度([Ca2+]i的影响及其信号转导机制.Fluo 3-AM标记酶消化法分离的单个心室肌细胞,用激光共聚焦显微镜测定细胞内[Ca2+]i的浓度.[Ca2+]i的变化用荧光强度(Fi)和相对荧光强度(Fi/F0%)表示.实验结果如下(1)在含Ca2+1.0 mmol/L的Tyrode's液中,CCK-8(1～104pmoVL)均可引起[Ca2+]i快速显著上升(P＜0.01).(2)用钙离子鳌合剂EGTA(3 mmol/L)和钙离子通道阻断剂nisoldipine(0.5μmol/L)预孵育心肌细胞5 min,CCK-8(102pmol/L)仅可引起[Ca2+]i缓慢轻度上升(P＜0.01).(3)用非选择性CCK受体拮抗剂丙谷胺(proglumide 6μmo1/L)或酪氨酸激酶抑制剂genistein(1 μmol/L)预孵育心肌细胞5 min,则完全抑制CCK-8诱导的[Ca2+]i升高(P＜0.01).CCK-8可通过激活其受体控制的Ca2+通道,引起Ca2+内流,诱导细胞内Ca2+释放,引起豚鼠单个心肌细胞内[Ca2+]i上升,此作用可能由酪氨酸激酶介导.     

腺苷减少豚鼠心室肌细胞内游离钙浓度

目的：研究腺苷对豚鼠心室肌细胞内游离钙浓度（[Ca^2＋]i）的影响并探讨其可能机制。方法：用激光共聚焦显微镜探测细胞内游离钙浓度,结果用相对荧光强度（（FI-FI0）／FI0,％;FI0：对照;FI：给药）表示。结果：①在正常台氏液和无钙台氏液中,腺苷（10,50,100μmol／L）浓度依赖性地降低[Ca^2＋];。②含30mmol／L KCl的台氏液（高钾台氏液）能够增加[Ca^2＋]i。腺苷（10,50,100μmol／L）能够显著抑制KCl引起的[Ca^2＋]i的增加。③预先应用选择性腺苷AI受体拮抗剂DPCPX（1μmol／L）,可大部分取消腺苷（100μmol／L）在高钾台氏液中的作用。腺苷（100μmol／L）在高钾台氏液的作用也可被预先应用一氧化氮（No）合酶抑制剂L-NAME（1mmol／L）所部分减弱。④腺苷（100μmol／L）能明显抑制无钙台氏液中由低浓度ryanodine引起的[Ca^2＋];增加。⑤当细胞外液钙浓度由1mmol／L增加到10mmol／L而诱发心室肌细胞钙超载时,部分心室肌细胞产生可传播的钙波,腺苷（100μmol／L）可降低钙波发生的频率和持续时间,最终阻断钙波并降低[Ca^2＋];。结论：腺苷可通过抑制外钙内流和减少肌浆网内钙释放从而降低[Ca^2＋],其减少外钙内流可能是由于腺苷A1受体介导的电压依赖性Ca^2＋通道的抑制,NO可能参与这一过程。     

牛磺酸对大鼠脑神经细胞内钙稳态的影响

目的和方法 :利用激光扫描共聚焦显微镜和双波长荧光分光光度计 ,分别观察牛磺酸对无血清培养的单个海马神经细胞和分散的新生大鼠脑神经细胞内Ca2 浓度 ([Ca2 ]i)的影响 ,并探讨牛磺酸调节神经细胞内钙稳态的作用机理。结果 :牛磺酸主要通过刺激细胞内钙库释放 ,在一定剂量范围内 (0 .0 2～ 6 .4mmol/L)使神经细胞[Ca2 ]i 轻微升高 ,在 0 .4mmol/L时的升钙作用最大 (升钙百分率为 12 .2 0 %± 1.2 4% )。在测定介质中加入钙离子载体A2 3187(10 μmol/L) ,使神经细胞内的钙离子浓度升高 ,若此时加入牛磺酸 (1.6mmol/L) ,则神经细胞内钙离子的浓度下降。结论 :牛磺酸对细胞内钙离子有双向调节作用 ,牛磺酸可能是通过对钙稳态的调节作用来阻止细胞内钙超载 ,保护神经细胞、并发挥其增强动物学习记忆等方面功能的。     

三羟异黄酮对豚鼠心室肌细胞内游离钙浓度的影响

用激光共聚焦显微镜观察研究三羟异黄酮(genistein,GST)对豚鼠心室肌细胞内游离钙浓度([Ca^2 ]i)的影响。结果用相对荧光强度(FI-F0／FX0,％)表示。实验结果显示,在正常台氏液、无钙台氏液和正常台氏液中加入3mmol／L EGTA后,GST(10～40μmol／L)浓度依赖性地降低细胞内钙浓度。蛋白酪氨酸磷酸酶抑制剂正钒酸钠(sodium orthovanadate)和L-型Ca^2 通道激动剂Bay K8644可部分抑制正常台氏液时GST的效应。当细胞外液钙浓度由1mmol／L增加到10mmol／L而诱发心室肌细胞钙超载时,部分心室肌细胞产生可传播的钙波,GST(40μmol／L)可降低钙波的传播速度和持续时间,最终阻断钙波。以上结果提示,GST降低心室肌细胞内游离钙浓度,此作用与其抑制电压依赖性Ca^2 通道、减弱酪氨酸激酶抑制和豚鼠心室肌细胞肌浆网内钙释放有关。     

膜钠钙交换蛋白和过氧化氢交互作用对细胞内钙稳态调控

本研究旨在阐明过氧化氢（H2O2）和膜钠钙交换蛋白相互作用对胞浆钙[Ca^2 ],的调控。在稳定表达钠钙交换蛋白CK1．4细胞上,用^45Ca同位素液闪计数法测定钠钙交换蛋白的活性;用fura-2荧光探针和340／380nm双兴奋波长荧光影像技术测定钙释放和[Ca^2 ]i。两因素两水平和三因素两水平正交分析表明10mmol/L H2O2与150mmol/L细胞外钠（[Na^ ]o,1mmol/L细胞外钙[Ca^2 ],相互作用或10mmol/L H2O2分别与150mmol/L[Na ]。或1[Na^ ]。激活钠钙交换蛋白,排出细胞内钙离子,降低[Ca2 ]i。当[Na^ ]。递减至0mmol/L时,10mmol/L H2O2直接抑制钠钙交换蛋白的活性,增加钙释放和升高[Ca2 ]i.在不同[Na^=},梯度中,10mmol/LH2O2对膜的钠钙交换活动和[Ca2 ],起双重调节作用,即抑制或增加钙内流和[Ca^2=]i.10mmol/L H2O2与膜钠钙交换蛋白和[Ca2 ]。相互作用对钠钙交换活动方向,钙释放和[Ca^2_]起负反馈谳节作用。     

大黄素升高豚鼠结肠带细胞[Ca~(2 )]_i的特征和GDP的抑制作用

利用Fluo -3荧光探针检测细胞内自由Ca2 浓度([Ca2 ]i),研究了大黄素升高豚鼠结肠带细胞[Ca2 ]i 的量—效关系和动态变化特征,及GDP和胞外Ca2 浓度对其的影响。较低浓度大黄素随药物浓度增加使[Ca2 ]i 显著升高 ,更高浓度大黄素有超最大抑制效应。GDP对大黄素升高细胞[Ca2 ]i 的抑制作用随其浓度增加而增强。GDP和胞外Ca2 浓度影响大黄素诱发的[Ca2 ]i 动态变化的结果表明 :GDP使[Ca2 ]i 峰消失 ,胞外无Ca2 导致[Ca2 ]i 随时间显著下降 ,大黄素升高[Ca2 ]i 作用趋向消失。     

Differential effects of progesterone and 17beta-estradiol on the Ca(2+) entry induced by thapsigargin and endothelin-1 in in situ endothelial cells

The effects of progesterone and 17beta-estradiol on Ca(2+) signaling in in situ endothelial cells were investigated using front-surface fluorometry of fura-2-loaded strips of porcine aortic valve. Progesterone inhibited the thapsigargin-induced sustained [Ca(2+)](i) elevation (IC(50)=33.9 microM, n=4), while 17beta-estradiol added a transient [Ca(2+)](i) elevation. Progesterone and 17beta-estradiol had no significant effect on the thapsigargin-induced [Ca(2+)](i) elevations in the absence of extracellular Ca(2+). A Mn(2+)-induced decline of fluorescent intensity at 360 nm excitation was accelerated by thapsigargin. This acceleration was completely reversed by progesterone, but not by 17beta-estradiol. Progesterone inhibited, and 17beta-estradiol enhanced the endothelin-1 (ET-1)-induced [Ca(2+)](i) elevation, while both had no effect on the ET-1-induced Ca(2+) release observed in the absence of extracellular Ca(2+) or in the pertussis toxin-treated strips. Progesterone and 17beta-estradiol thus had different effects on Ca(2+) signaling, especially on Ca(2+) influx, in endothelial cells.     

Roles of Ca2+ and protein kinase C in the excitatory response to serotonin in embryonic molluscan ciliary cells

We examined the roles of Ca2+ and protein kinase C (PKC) in the cilio-excitatory response to serotonin in pedal ciliary cells from Helisoma trivolvis embryos. Serotonin (5-hydroxytryptamine; 5-HT; 100 micromol/L) induced an increase in ciliary beat frequency (CBF) was abolished by microinjected BAPTA (50 mmol/L), but was only partially inhibited by the phospholipase C inhibitor U-73122 (10 micromol/L). The diacylglycerol analogs 1-oleoyl-2-acetyl-sn-glycerol (100 micromol/L) and 1,2-dioctanoyl-sn-glycerol (100 micromol/L) caused increases in [Ca2+]i that were smaller than those induced by serotonin. In the absence of extracellular Ca2+, 1,2-dioctanoyl-sn-glycerol (100 micromol/L) failed to elicit an increase in both CBF and [Ca2+]i. In contrast, the serotonin-induced increase in CBF persisted in the absence of extracellular Ca2+, although the increase in [Ca2+]i was abolished. PKC inhibitors bisindolylmaleimide (10 and 100 nmol/L) and calphostin C (10 nmol/L) partially inhibited the serotonin-induced increase in CBF, but didn't affect the serotonin-induced change in [Ca2+]i. These findings suggest that an intracellular store-dependent increase in [Ca2+]i mediates the cilio-excitatory response to serotonin. Furthermore, although PKC is able to cause an increase in [Ca2+]i through calcium influx, it contributes to the cilio-excitatory response to 5-HT through a different mechanism.     

Regulation by clozapine of calcium handling by rat submandibular acinar cells

The effect of clozapine on the intracellular concentration of calcium ([Ca2+](i)) in rat submandibular acinar cells was tested. By itself clozapine had no effect on the mobilization of intracellular pools of calcium or on the uptake of extracellular calcium. It inhibited the increase of the [Ca2+](i) in response to carbachol (half-maximal inhibitory concentrations, IC(50)=100nM) and to norepinephrine and epinephrine (IC(50)=10nM) without affecting the response to substance P, extracellular ATP or thapsigargin. Clozapine inhibited the uptake of extracellular calcium in response to epinephrine but not to substance P, ATP or thapsigargin. It also decreased the production of inositol phosphates elicited by epinephrine but not by substance P or fluoride. It is concluded that, by itself, clozapine has no effect on the [Ca2+](i) in rat salivary acinar cells. It selectively inhibits muscarinic and adrenergic receptors in the acinar plasma membrane.     

Capsazepine elevates intracellular Ca2+ in human osteosarcoma cells, questioning its selectivity as a vanilloid receptor antagonist

Capsazepine is thought to be a selective antagonist of vanilloid type 1 receptors; however, its other in vitro effect on different cell types is unclear. In human MG63 osteosarcoma cells, the effect of capsazepine on intracellular Ca(2+) concentrations ([Ca(2+)](i)) and cytotoxicity was explored by using fura-2 and tetrazolium, respectively. Capsazepine caused a rapid rise in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 100 microM. Capsazepine-induced [Ca(2+)](i) rise was partly reduced by removal of extracellular Ca(2+), suggesting that the capsazepine-induced [Ca(2+)](i) rise was composed of extracellular Ca(2+) influx and intracellular Ca(2+). In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic [Ca(2+)](i) rise, after which the increasing effect of capsazepine on [Ca(2+)](i) was inhibited by 75%. Conversely, pretreatment with capsazepine to deplete intracellular Ca(2+) stores totally prevented thapsigargin from releasing more Ca(2+). U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca(2+) mobilizer)-induced, but not capsazepine-induced, [Ca(2+)](i) rise. Overnight treatment with 1-100 microM capsazepine inhibited cell proliferation in a concentration-dependent manner. These findings suggest that in human MG63 osteosarcoma cells, capsazepine increases [Ca(2+)](i) by stimulating extracellular Ca(2+) influx and also by causing intracellular Ca(2+) release from the endoplasmic reticulum via a phospholiase C-independent manner. Capsazepine may be mildly cytotoxic.     

Muscarinic receptors modulate intracellular Ca2+ concentration in hyaline cells of the chicken basilar papilla

Nonsensory hyaline cells border the sensory epithelium of the auditory end-organ (basilar papilla) in birds and reptiles. Their innervation by cochlear cholinergic efferent fibers and the presence of contractile proteins suggest that hyaline cells may actively regulate basilar membrane mechanics. The cholinergic pharmacology of hyaline cells was studied by measuring the intracellular calcium concentration ([Ca(2+)](i)) of fura-2-loaded cells in the chicken cochlea in vitro. Superfusion of the cholinergic agonist carbachol produced a dose-dependent increase in hyaline cell [Ca(2+)](i) (EC(50)=1.05 micromol l(-1)) and small responses in short hair cells. Calcium increases in hyaline cells were evoked by the muscarinic agonists oxotremorine (10 micromol l(-1)) and muscarine (100 micromol l(-1)) whereas nicotine (100 micromol l(-1), 200 micromol l(-1)) was without effect. Carbachol-evoked responses were blocked by the muscarinic antagonist atropine (>or=10(-13) mol l(-1)) and were unaffected by the nicotinic antagonists d-tubocurare (100 micromol l(-1), 1 mmol l(-1)) and hexamethonium (100 micromol l(-1)). Responses persisted in the absence of extracellular Ca(2+) and were abolished by thapsigargin (1 micromol l(-1)). These results indicate that the cholinergic-stimulated increase in hyaline cell [Ca(2+)](i) is due to a muscarinic-mediated release of Ca(2+) from intracellular stores. This is the first evidence that hyaline cells possess a muscarinic receptor whose activation causes mobilization of intracellular Ca(2+).     

Ca(2+) entry into primary cultured pig coronary smooth muscle cells after previous store depletion by repetitive P2Y purinoceptor stimulation

Store-operated Ca(2+) entry, stimulated by depletion of intracellular Ca(2+) pools, has not been fully elucidated in vascular smooth muscle cells of pig coronary arteries. Therefore, [Ca(2+)](i) was measured in cultured cells derived from extramural pig coronary arteries using the Fura-2/AM fluorometry. Divalent cation entry was visualized with the Fura-2 Mn(2+)-quenching technique. Ca(2+) stores were depleted either by repetitive stimulation of P2Y purinoceptors with ATP (10 micromol/L), or by the sarcoendoplasmic Ca(2+)-ATPase inhibitor 2,5-Di-(tert-butyl)-1,4-benzohydroquinone (BHQ; 1 micromol/L) in Ca(2+)-free medium (EGTA 1 mmol/L). Addition of Ca(2+)(1 mmol/L) induced refilling of ATP-sensitive Ca(2+) stores and an increase in [Ca(2+)](i) in the presence of BHQ. Both could be significantly diminished by Ni(2+)(5 and 1mmol/L), La(3+)(10 micromol/L), Gd(3+)(10 micromol/L), and Mg(2+)(5.1 mmol/L). In contrast to the BHQ-mediated rise in [Ca(2+)](i), refilling of ATP-depleted stores was affected by neither flufenamate (0.1 mmol/L), nor by nitrendipine, nifedipine, and nisoldipine (each 1 micromol/L). The data suggest that after store depletion in pig coronary smooth muscle cells ATP and BHQ may converge on a common, Ni(2+)-, La(3+)-, Gd(3+)-, and Mg(2+)- sensitive Ca(2+) entry pathway, i.e. on a store-operated Ca(2+) entry. An additional contribution of the Na(+)/Ca(2+) exchanger cannot be excluded. Flufenamate-sensitive non-selective cation channels and dihydropyridine-sensitive L-type Ca(2+) channels are not involved in refilling of Ca(2+) stores after previous depletion by repetitive P2Y purinoceptor stimulation. The store-operated Ca(2+) entry in-between repetitive purinoceptor stimulation, i.e. in the absence of the agonist, may be responsible for the maintenance of agonist-induced rhythmic Ca(2+) responses.     

Effects of N-n-butyl haloperidol iodide on L-type calcium channels and intracellular free calcium in rat ventricular myocytes.

The ability of N-n-butyl haloperidol iodide (F2) to cause vasodilation, and thereby produce a cardioprotective effect, has been well documented. The aim of this study was to investigate whether F2 might act as a Ca2+ antagonist. Myocytes were obtained from rat heart, and the whole-cell patch-clamp technique was used to record Ca2+ current. Laser scanning confocal microscopy was used to measure intracellular free calcium ([Ca2+]i). The results obtained from this study demonstrate that F2 reduced calcium current (ICa) in a concentration-dependent manner with an IC50 of 1.19 micromol/L, upshifted the current-voltage curve of ICa, shifted the inactivation kinetics of ICa leftward, and slowed down the recovery of ICa from inactivation. F2 decreased the fluorescent intensity of [Ca2+]i elevation induced by KCl with an IC50 of 1.61 micromol/L, and had no effects on the intracellular calcium release induced by caffeine and inositol-1,4,5-trisphosphate. These findings indicate that F2 may act as a calcium antagonist, which could account for its cardiovascular benefits.     

Reconstitution of the basal calcium transport in resealed human red blood cell ghosts

The (45)Ca(2+) influx into right-side-out resealed ghosts (RG) prepared from human red blood cells (RBC) was measured. The (45)Ca(2+) equilibration occurred with t(1/2)=2.5 min and the steady-state was reached after 17 min with the level of 22+/-2 micromol/L(packed cells) at 37 degrees C. The rate of the influx was 97+/-17 micromol/L(packed cells)h. The (45)Ca(2+) influx was saturated with [Ca(2+)](0) at 4 mmol/L and was optimal at pH 6.5 and 30 degrees C. Divalent cations (10(-4)-10(-6)mol/L), nifedipine (10(-5)-10(-4)mol/L), DIDS (up to 10(-4)mol/L), and quinidine (10(-4)-10(-3)mol/L), inhibited the (45)Ca(2+) influx while uncoupler (10(-6)-10(-5)mol/L) stimulated it. In contrast to intact RBC, vanadate inhibited the (45)Ca(2+) influx when added to the external medium, however, the stimulation was observed when vanadate was present in media during both lysis and resealing. PMA had no effect under conditions found to stimulate the Ca(2+) influx in intact RBC. The results show that the Ca(2+) influx into RG is a carrier-mediated process but without control by protein kinase C and that the influx and efflux of Ca(2+) are coupled via the H(+) homeostasis similarly as in intact RBC but with modified mechanism.