An estimate of rapid cytoplasmic calcium buffering in a single smooth muscle cell
An estimate of rapid cytoplasmic calcium buffering in a single smooth muscle cell
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DOI：
10.1054/ceca.1999.0084
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发表时间：
2000-01-01
期刊：
影响因子：
4
通讯作者：
Ganitkevich, VY
中科院分区：
文献类型：
--
作者：
Daub, B;Ganitkevich, VY
用低亲和荧光团Indo-1FF测定了豚鼠膀胱单离体平滑肌细胞中sarco （endo）质网功能缺失时细胞质钙的增加。为了评估肌浆的Ca2+缓冲特性，以i - ca的时间积分（积分i - ca）测量的Ca2+内流与细胞质中相应的游离Ca2+增量（δ [Ca2+](i)）进行了比较。积分i - ca和δ [Ca2+](i)的比值（积分i - ca / δ [Ca2+](i)）在4.9-9.3 pC/mu M（平均6.2 +/- 1.2,n = 12）之间，反映了胞质溶胶的Ca2+缓冲性能。在长达25分钟的记录期间，它保持大约恒定（6.4 +/- 1.4 pC/mu M, n = 8），这表明细胞质Ca2+结合在细胞透析期间没有显着改变，并且内源性Ca2+缓冲液没有通过贴片移液管明显地从细胞中冲洗出来。BAPTA（一种可移动的高亲和力Ca2+缓冲液）进入或流出细胞，在几分钟内显著改变了Ca2+通过Ca2+通道流入和δ [Ca2+](i)之间的关系。在去极化过程中，i - ca / δ [Ca2+](i)的变化使游离[Ca2+](i)增加至5 μ M，这表明快速Ca2+缓冲液的表观亲和力下限（16 μ M）和总缓冲液浓度下限（530 μ M）。将4 mM DPTA （K-d for Ca2+ = 81 mu M）引入细胞，使细胞质Ca2+缓冲容量增加了一倍以上。这些结果表明，平滑肌细胞的细胞质Ca2+缓冲液对游离Ca2+具有低亲和力。大多数细胞的细胞质Ca2+结合比率估计在30到40之间。Ca2+结合率在新生儿（小于或等于5天）和成年动物分离的细胞之间没有显着差异。(C)哈考特出版有限公司2000。
Cytoplasmic calcium increments in the absence of sarco (endo) plasmic reticulum function were measured with a low-affinity fluorophore Indo-1FF in single isolated smooth muscle cells from guinea-pig urinary bladder. To evaluate the Ca2+-buffering properties of the myoplasm, Ca2+ influx, measured as time integral of the I-Ca (integral I-Ca), was compared with corresponding free Ca2+ increments (Delta[Ca2+](i)) in the cytoplasm. The ratio between integral I-Ca and Delta[Ca2+](i) (integral I-Ca/Delta[Ca2+](i)), reflecting the Ca2+ buffering properties of the cytosol, was in the range of 4.9-9.3 pC/mu M (mean 6.2 +/- 1.2, n = 12). It remained approximately constant (6.4 +/- 1.4 pC/mu M, n = 8) during recordings lasting up to 25 min, suggesting that cytoplasmic Ca2+ binding does not change markedly during cell dialysis and that the endogenous Ca2+ buffer is not significantly washed out of the cell through the patch pipette. Wash-in or wash-out of BAPTA, a mobile high-affinity Ca2+ buffer, into or from the cell markedly changed the relationship between Ca2+ influx through Ca2+ channels and Delta[Ca2+](i) within minutes. Changes in integral I-Ca/Delta[Ca2+](i) during the sequence of depolarizing steps, which increased free [Ca2+](i) up to 5 mu M, suggested lower limits for the apparent affinity of a rapid Ca2+ buffer (16 mu M) and for the total buffer concentration (530 mu M). Introduction of 4 mM DPTA (K-d for Ca2+ = 81 mu M) into the cell more than doubled the total cytoplasmic Ca2+ buffer capacity. These results suggest that cytoplasmic Ca2+ buffer in smooth muscle cells has a low affinity for free Ca2+. The Ca2+-binding ratio of the cytoplasm in most cells was estimated to be between 30 and 40. The Ca2+-binding ratio did not differ markedly between cells isolated from neonatal (less than or equal to 5 days) and adult animals. (C) Harcourt Publishers Ltd 2000.