CA CONCENTRATION AND FLUX IN CA-DEPRIVED ARTERIES
CA CONCENTRATION AND FLUX IN CA-DEPRIVED ARTERIES
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DOI：
10.1113/jphysiol.1972.sp009880
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发表时间：
1972-01-01
影响因子：
5.5
通讯作者：
KEATINGE, WR
中科院分区：
文献类型：
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作者：
KEATINGE, WR
1.根据~(45)Ca和[~(14)C]EDTA洗脱研究，估算了无钙和无钙溶液中动脉平滑肌细胞外钙和EDTA的浓度。根据给定时刻测量的~(45)Ca洗脱速率，结合单独测定组织中钙的扩散系数，计算出CA浓度，而通过分析[14C]EDTA洗脱的指数阶段来计算EDTA浓度，并通过单独测定EDTA在组织中的扩散系数来检查。在36°C的无钙生理盐水中，30min后细胞外钙浓度在组织中心为0.049 mM，整个组织平均为0.033 mM，远高于去除组织内钙储备后收缩的阈值-0.05 mM-Ca。在36°C EDTA12.5mMMat或5°C下4.9min，细胞外EDTA浓度在1.9min后达到6.25mM，在5°C下30min后达到12.45mM，足以使组织中的细胞外游离钙保持在远低于阈值的水平，即使组织中所有的钙都在升温时突然释放，以0.42mMole/g为单位。3.组织中心的细胞外钙浓度在36℃的EDTA12.5mMMat或5°C的4.9min后达到6.25mM，在5°C的30min后达到12.45mM，即使组织中所有的钙都被突然释放，被测得为0.42mole/g。在冷EDTA中放置较长时间后，组织钙外流显著增加，在36°C的EDTA中，所有可测钙都在30min内离开组织，而组织中的镁在此期间没有显著下降。去甲肾上腺素在无钙生理盐水中引起的收缩，无论有没有乙二胺四乙酸乙二胺存在，都与外部钙丢失速率大于0.001μ摩尔的任何增加无关，例如−1.min−1.6.电子显微镜下可见许多与细胞外间隙连通的微泡；光滑的内质网以及可能含有非连通钙库的其他结构。结果表明，动脉对去甲肾上腺素在无钙生理盐水中的较大反应是由于维持细胞外钙或依赖于此的不稳定的钙库，而在冷EDTA中长时间的小反应依赖于非通信性的钙库，这些钙库的损失与温度有关，不能被扩散所限制。
1. Extracellular Ca and EDTA concentrations in arterial smooth muscle in Ca‐free solutions with and without EDTA were estimated from45Ca and [14C]EDTA washout studies. Ca concentrations were calculated from the measured rate of45Ca washout at a given moment, combined with separate determinations of the coefficient of diffusion of Ca in the tissue, while EDTA concentrations were calculated by analysing an exponential phase of [14C]EDTA washout and checked by separate determinations of coefficient of diffusion of EDTA in the tissue.2. Extracellular Ca concentrations after 30 min in simple Ca‐free saline at 36° C was 0·049 mMat the centre of the tissue and averaged 0·033 mMthroughout the tissue; these were well above the value of 0·005 mM‐Ca that was found to be the threshold external level for contraction after tissue stores of Ca were removed.3. Extracellular EDTA concentration at the centre of the tissue reached 6·25 mMafter 1·9 min in EDTA 12·5 mMat 36° C or after 4·9 min at 5° C. It reached 12·45 mMafter 30 min at 5° C, enough to keep free extracellular Ca at this point well below threshold even if all of the Ca in the tissue, determined as 0·42 μmole/g, were suddenly released on warming.4. Ca efflux increased greatly on warming after long periods in cold EDTA, and all measurable Ca left the tissue within 30 min in EDTA 12·5 mMat 36° C although tissue Mg did not fall significantly during this time.5. Contractions elicited by noradrenaline in Ca‐free saline, with or without EDTA present, were not associated with any increases in the rate of external loss of Ca greater than 0·001 μmole.g−1.min−1.6. Electronmicrographs showed numerous microvesicles that communicated with the extracellular space; also smooth endoplasmic reticulum among other structures that might have contained non‐communicating Ca stores.7. The results provide evidence that large responses given by the arteries to noradrenaline in simple Ca‐free saline were due to persisting extracellular Ca or to labile Ca stores dependent on this, while small responses obtained after long periods in cold EDTA depended on non‐communicating Ca stores whose loss was too temperature‐dependent to be limited by diffusion.