丹皮酚对体外培养乳鼠心肌细胞~(45)Ca摄取的影响

通过测定体外培养乳鼠心肌细胞~(45)Ca摄取及其搏动频率的变化,观察丹皮酚对心肌细胞Ca~(2+)内流的影响。结果50～400μg/ml的丹皮酚,能显著降低心肌细胞搏动频率,对心肌细胞快相(5min)和慢相(120min)~(45)Ca摄取均有显著抑制作用,且400μg/ml丹皮酚与10μmol/L的维拉帕米的作用相似。提示丹皮酚能抑制心肌细胞的Ca~(2+)内流,可能与阻滞慢钙通道有关。     

丹皮酚磺酸钠对钙反常培养乳鼠心肌细胞Ca2+内流的抑制作用

培养乳鼠心肌细胞复制钙反常模型,观察丹皮酚磺酸钠对心肌细胞⁴⁵Ca摄取、膜唾液酸(SA)含量及细胞搏动频率的影响,结果提示丹皮酚磺酸钠在50～400μg/ml范围内能显著抑制正常心肌细胞快相(5 min)和慢相(120 min)⁴⁵Ca摄取及其搏动频率,且能显著抑制钙反常心肌细胞的⁴⁵²⁺内流外,尚与其提高膜SA含量有关。     

Increase in catecholamine release and 45Ca2+ uptake induced by GABA in cultured bovine adrenal chromaffin cells

The role of Ca2+ in GABA-evoked catecholamine (CA) release from adrenal medulla was investigated in primary cultures of bovine adrenal chromaffin cells. GABA facilitated the 45Ca2+ uptake associated with the increase of Ca release in cultured bovine adrenal chromaffin cells. The effects of GABA on both 45Ca2+ uptake and CA release were blocked by bicuculline and picrotoxin. Nifedipine reduced the 45Ca2+ uptake and CA release induced by GABA. These data support our previous suggestion that the activation of GABA receptors on adrenal chromaffin cells facilitates the Ca2+ influx through voltage-sensitive Ca2+ channels, leading to the release of CA.     

山豆根碱对大鼠血小板摄取~（45）Ca~（2＋）的影响

用４５Ｃａ２＋摄入法测定了大鼠血小板摄取细胞外Ｃ２＋，观察山豆根碱对血小板摄取Ｃａ２＋的影响、结果表明，静息血小板可迅速摄取细胞外Ｃａ２＋，呈时间和浓度依赖性；ＡＤＰ促进血小板摄取Ｃａ２＋；山豆根碱以浓度依赖方式抑制静息的和ＡＤＰ诱导的血小板摄取细胞外Ｃａ２＋。这提示山豆根碱抑制血小板聚集的作用机制之一与阻止细胞外Ｃａ２＋内流入血小板，降低血小板胞浆内Ｃａ２＋浓度有关。     

前胡丙素对培养心肌细胞~（45）Ca~（2＋）摄入及细胞内游离钙的影响

利用培养的乳鼠心肌细胞测定细胞４５Ｃａ２＋的摄入及细胞内游离钙的浓度。结果表明，前胡丙素（Ｐｒａ－Ｃ）１０－１００μｍｏｌ·Ｌ－１依浓度抑制４５Ｃａ２＿的摄入，并抑制由３０μｍｏｌ·Ｌ－１ＫＣｌ所引起的４５Ｃｓ２＋摄入的增加，同时Ｐｒａ－Ｃ１００μｍｏｌ·Ｌ－１对去甲肾上腺素所诱发的４５Ｃａ２＿摄入的增加也有抑制作用。Ｐｒａ－Ｃ１０μｍｏｌ·Ｌ－１和维拉帕米１０μｍｏｌ·Ｌ－１能抑制细胞外高钾（３０，５０ｍｍｏｌ·Ｌ－１）引起的［Ｃａ２＋］ｉ的升高，同时Ｐｒａ－Ｃ３０ｍｏｌ·Ｌ－１和维拉帕米１０μｍｏｌ·Ｌ－１对去甲肾上腺素１０μｍｏｌ·Ｌ－１在无钙及含ＣａＣｌ２１．３ｍｍｏｌ·Ｌ－１的溶液中所引起的［Ｃａ２＋］，的增加也有抑制作用。提示前胡丙素对心肌细胞的作用与其阻滞钙通道有关。     

Maitotoxin-induced myocardial cell injury: calcium accumulation followed by ATP depletion precedes cell death

Maitotoxin, the most potent marine toxin, is known to increase the uptake and the accumulation of Ca2+ into cells, and was used in the present study to investigate the mechanisms of myocardial cell damage induced by Ca2+ overload. In cultured cardiomyocytes, isolated from 2-day-old rats, maitotoxin affected cell viability, as indicated by the leakage of the cytosolic enzyme lactate dehydrogenase (LDH) and of radiolabeled adenine nucleotides into the extracellular medium. Maitotoxin-induced leakage of LDH steadily increased between 30 min and 24 hr, and was preceded by a marked depletion of intracellular ATP. Addition of maitotoxin resulted in a rapid influx of extracellular Ca2+, as detected by preincubating the cells in the presence of 45Ca; this effect evolved in a few minutes, thus preceding the signs of cell death. Cytosolic levels of free Ca2+ ([Ca2+]i) were monitored by loading freshly isolated, suspended cardiomyocytes with the intracellular fluorescent probe fura-2; in these cells, maitotoxin induced a dose-dependent increase in [Ca2+]i, with a lag phase of less than a minute. All these effects of maitotoxin were inhibited by reducing Ca2+ concentration in the culture medium or by incubating the cells with the calcium-channel blocking drug verapamil. It is thus demonstrated that maitotoxin-induced cardiotoxicity is secondary to an inordinate influx of Ca2+ into the cells. It is also suggested that, in those conditions that lead to an inordinate accumulation of Ca2+ into myocardial cells, the unmatched demands of energy and the depletion of ATP play a primary role in the irreversible stage of cell damage.     

Characterization of interactions of methylmercury with Ca2+ channels in synaptosomes and pheochromocytoma cells: radiotracer flux and binding studies

The interaction of methylmercury (MeHg) with neuronal Ca2+ channels in rat forebrain synaptosomes and dihydropyridine (DHP)-sensitive Ca2+ channels in rat pheochromocytoma (PC12) cells was examined using radiotracer flux assays and radioligand binding analyses. In synaptosomes, the influx of 45Ca2+ was used to examine the voltage and state dependence of block of Ca2+ channels by MeHg, as well as the effects of MeHg on apparent inactivation of 45Ca2+ influx. In addition, the differential influx of 45Ca2+, 85Sr2+, and 133Ba2+ was used to examine the effect of MeHg on the ionic selectivity of synaptosomal Ca2+ channels. The ability of MeHg to block 45Ca2+ influx via a DHP-sensitive Ca2+ channel was examined in PC12 cells. Effects of MeHg on binding of [3H]nitrendipine in synaptosomes and 125I-omega-conotoxin GVIA (CgTx) in synaptosomes and PC12 cells were measured. In synaptosomes, MeHg blocked 45Ca2+ influx in a voltage-dependent manner, inasmuch as increasing the extracellular K+ concentration increased the magnitude of block by 100 microM MeHg. When synaptosomes were incubated for 10 sec in either a nondepolarizing or a depolarizing solution before measurement of 1 sec of depolarization-induced 45Ca2+ influx, the potency and efficacy of the block of 45Ca2+ influx by MeHg were similar. Thus, block of Ca2+ channels by MeHg does not appear to be state dependent. To determine the kinetics of apparent inactivation of 45Ca2+ influx, synaptosomes were predepolarized in Ca2(+)-free high [K+] solution, for intervals varying from 1 to 10 sec, before measurement of 1 sec of K(+)-induced 45Ca2+ influx. When compared with control, MeHg (100 microM) altered the rate constant for apparent inactivation and decreased the fraction of 45Ca2+ influx that does not inactivate. Influx of 45Ca2+, 85Sr2+, and 133Ba2+ during 1 sec of depolarization was blocked in a dose-dependent manner by MeHg, with estimated IC50 values of 125, 150, and greater than 150 microM for 45Ca2+, 85Sr2+, and 133Ba2+, respectively. In triple-label experiments, the relative flux of radiolabeled Ca2+:Sr2+:Ba2+ was altered from approximately 6:2:3 to 6:1:3 in the presence of 100 microM MeHg. In undifferentiated and nerve growth factor-differentiated PC12 cells, K(+)-induced 45Ca2+ influx was blocked by the DHP nifedipine, with an approximate IC50 value of 5 nM. MeHg reduced 45Ca2+ influx in PC12 cells with an estimated IC50 value of 50 microM, and 125 microM MeHg reduced uptake by greater than 90%. [3H]Nitrendipine bound to synaptosomes with high affinity in normal and elevated [K+] solutions.(ABSTRACT TRUNCATED AT 400 WORDS)     

三七总皂苷对大鼠星状神经节后超极化电位的影响

目的研究三七总皂苷(PNS)对神经元放电频率的影响是否与改变膜电位的超极化程度有关。方法向大鼠星状神经节(SG)细胞内输入去极化电流,诱发动作电位,区分相位式发放(phasic)细胞和紧张式发放(ton ic)细胞,观察PNS灌流SG后,细胞放电类型和放电频率、后超极化电位(AHP)、高钙易化的快兴奋性突触后电位(f-EPSP)的变化。结果PNS使ton ic细胞重复发放的频率下降。在0.12~0.16 g.L-1浓度范围内,PNS对SG细胞的AHP有浓度依赖性抑制作用。PNS还能可逆性拮抗高钙对f-EPSP的易化作用。结论PNS降低大鼠SG细胞的放电频率并非通过强化AHP电位引起,PNS对神经细胞兴奋性的抑制是因拮抗胞膜钙内流所致。     

维拉帕米对CVB_3感染心肌细胞Ca~(2+)内流及CVB_3-RNA含量的影响

观察了维拉帕米(Verapamil,Ver)对感染柯萨奇B_3病毒(CVB_3)的大鼠培养心肌细胞Ca~(2+)内流及CVB_3-RNA复制的影响。结果发现在感染48h后,Ver对感染细胞及正常对照的Ca~(2+)内流均有显著的抑制作用(P<0.01);若在病毒感染同时加入Ver,经48h培养后,细胞中CVB_3-RNA含量显著高于病毒对照组(P<0.05)。提示钙拮抗剂(如Ver)可减少病毒感染引起的心肌Ca~(2+)内流增加,有可能减轻感染细胞的继发性Ca~(2+)损伤;但Ver会促进病毒RNA的复制,提示在急性病毒性心肌炎临床上用Ver治疗心律失常时宜慎重。