TOTAL CYTOPLASMIC CALCIUM IN RELAXED AND MAXIMALLY CONTRACTED RABBIT PORTAL-VEIN SMOOTH-MUSCLE
TOTAL CYTOPLASMIC CALCIUM IN RELAXED AND MAXIMALLY CONTRACTED RABBIT PORTAL-VEIN SMOOTH-MUSCLE
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DOI：
10.1113/jphysiol.1984.sp015496
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发表时间：
1984-01-01
影响因子：
5.5
通讯作者：
SOMLYO, AV
中科院分区：
文献类型：
--
作者：
BOND, M;SHUMAN, H;SOMLYO, AV
通过对兔门肠系膜前静脉条进行电子探针微量分析来测量血管平滑肌中总细胞质 Ca 的浓度，该条在放松时或在高 K 和去甲肾上腺素 [去甲肾上腺素] 刺激的维持（30 分钟）最大收缩期间快速冷冻。在无钙、高镁溶液中孵育后，将试纸条冷冻并进行分析。 0.1-0.2μm和1.0-1.5μm的探针直径分别用于测量细胞质和细胞（包括储存的）Ca。细胞质 Ca 显着增加 (P < 0.0005) 1.0 .+-。 0.2 (SD) mmol Ca/kg 干重 0.8 .+-。 0.2（平均值 SE）mmol/kg 干重（n = 262 个谱图，6 只动物）至 1.8.+-。最大收缩期间为 0.2（平均值 SE）mmol Ca/kg 干重（n = 296 个光谱，6 只动物）。这种增加大于与钙调蛋白和肌球蛋白结合的 Ca2+ 所能解释的增加，表明平滑肌中存在其他 Ca2+ 结合蛋白。在无 Ca、高 Mg2+ EGTA [乙二醇-双（β-氨基乙基醚）-N,N''-四乙酸]溶液中孵育后，残留少量（0.4-0.6 mmol/kg 干重）细胞质 Ca。这种紧密结合的细胞质 Ca 不足以解释已知与 F-肌动蛋白结合的二价阳离子的总量。镁是平滑肌和横纹肌中 F-肌动蛋白中主要的不可交换结合的阳离子。在收缩的肌肉中，用包含储存在肌浆网 (s.r.) 中的 Ca 的大探针测量的细胞 Ca 浓度为 3.2 .+-。 0.3（平均值 SE）mmol Ca/kg 干重 (n = 93)，显着高于用小探针测量的细胞质 Ca 浓度。细胞 Ca 的值可能被低估，因为大直径探针没有覆盖所有的外围 s.r。细胞 Ca（用大探针测量）在收缩组织中最高，在松弛组织中较低，并且在无 Ca 溶液中孵育的肌肉中显着减少。在收缩的肌肉中，细胞质镁显着减少，线粒体镁增加。在0 Ca、高Mg2+溶液中，细胞质Mg显着增加。线粒体 Ca 在维持收缩期间没有显着变化，但在无 Ca、高 Mg2+ 溶液中孵育后显着低于正常含 Ca 溶液中的松弛组织 (1.6.+-. 0.2 mmol Ca/kg 干重) (0.0.+-. 0.2 (平均值 SE) mmol Ca/kg 干重)。
The concentration of total cytoplasmic Ca in vascular smooth muscle was measured by electron probe microanalysis of strips of rabbit portal anterior mesenteric vein that were rapidly frozen either when relaxed or during a maintained (30 min) maximal contraction stimulated with high K and noradrenaline [norepinephrine]. Strips were also frozen and analyzed after incubation in Ca-free, high-Mg2+ solution. Probe diameters of 0.1-0.2 .mu.m and 1.0-1.5 .mu.m were used to measure, respectively, cytoplasmic and cellular (including stored) Ca. There was a highly significant increase (P < 0.0005) in cytoplasmic Ca of 1.0 .+-. 0.2 (SD) mmol Ca/kg dry wt from 0.8 .+-. 0.2 (SE of mean) mmol/kg dry wt (n = 262 spectra, 6 animals) to 1.8 .+-. 0.2 (SE of mean) mmol Ca/kg dry wt (n = 296 spectra, 6 animals) during maximal contraction. This increase was greater than can be accounted for by Ca binding to calmodulin and to myosin, suggesting the presence of other Ca-binding proteins in smooth muscle. A small amount (0.4-0.6 mmol/kg dry wt) of cytoplasmic Ca remained after incubation in Ca-free, high-Mg2+ EGTA [ethyleneglycol-bis(.beta.-aminoethylether)-N,N''-tetraacetic acid] solution. This tightly bound, cytoplasmic Ca was insufficient to account for the total amount of divalent cation known to be bound to F-actin. Mg is the major inexchangeably bound cation in F-actin in smooth as in striated muscle. In the contracted muscles, the cellular Ca concentration, measured with the large probes that include Ca stored in the sarcoplasmic reticulum (s.r.), was 3.2 .+-. 0.3 (SE of mean) mmol Ca/kg dry wt (n = 93), significantly higher than the cytoplasmic Ca concentration measured with small probes. This value of cellular Ca was probably an underestimate, as the large-diameter probes did not cover all of the peripheral s.r. The cellular Ca (measured with large probes) was highest in the contracted and lower in the relaxed tissue, and was significantly reduced in the muscles incubated in Ca-free solution. In contracted muscle, cytoplasmic Mg significantly decreased and mitochondrial Mg increased. In 0 Ca, high-Mg2+ solution, the cytoplasmic Mg increased significantly. Mitochondrial Ca did not significantly change during a maintained contraction, but was significantly lower (0.0 .+-. 0.2 (SE of mean) mmol Ca/kg dry wt) after incubation in Ca-free, high-Mg2+ solution than in the relaxed tissue (1.6 .+-. 0.2 mmol Ca/kg dry wt) in normal Ca-containing solution.