Varro A, Negretti N, Hester S B, Eisner D A
Department of Veterinary Preclinical Sciences, University of Liverpool, UK.
Pflugers Arch. 1993 Apr;423(1-2):158-60. doi: 10.1007/BF00374975.
The aim of this paper was to estimate the Ca content of the sarcoplasmic reticulum (s.r.) and to compare this with the amount of Ca which enters the cell via the calcium current in systole. The s.r. Ca content was measured electrophysiologically in voltage-clamped rat ventricular myocytes. Rapid application of caffeine produced a transient increase of [Ca2+]i which was accompanied by a transient inward Na-Ca exchange current. The integral of this current gives a measure of the Ca2+ pumped out of the cell by Na-Ca exchange. Ni2+ (5 mM) inhibited the current and decreased the rate of fall of [Ca2+]i to 32% of the control suggesting that Na-Ca exchange is responsible for 68% of Ca removal from the cytoplasm following the addition of caffeine. Correcting for the Na-Ca independent Ca removal suggests that the s.r. Ca content is equivalent to about 120 mumol per litre cell. Furthermore we estimate that, during systole, Ca entry into the cell via the sarcolemmal calcium current is equal to about 6% of the Ca content of the s.r.
本文的目的是估计肌浆网（s.r.）的钙含量，并将其与在收缩期通过钙电流进入细胞的钙量进行比较。在电压钳制的大鼠心室肌细胞中用电生理学方法测量肌浆网钙含量。快速施加咖啡因会使[Ca2+]i短暂增加，同时伴有短暂的内向钠钙交换电流。该电流的积分可衡量通过钠钙交换泵出细胞的Ca2+量。Ni2+（5 mM）抑制该电流，并使[Ca2+]i的下降速率降至对照的32%，这表明在添加咖啡因后，钠钙交换负责68%的细胞质钙清除。校正与钠钙无关的钙清除后表明，肌浆网钙含量约相当于每升细胞120微摩尔。此外，我们估计，在收缩期，通过肌膜钙电流进入细胞的钙约等于肌浆网钙含量的6%。
