Negretti N, O'Neill S C, Eisner D A
Department of Veterinary Preclinical Sciences, University of Liverpool, United Kingdom.
Cardiovasc Res. 1993 Oct;27(10):1826-30. doi: 10.1093/cvr/27.10.1826.
The aim was to estimate the relative contributions of the various intracellular and sarcolemmal systems to the relaxation of the systolic calcium transient.
The experiments were performed on isolated rat ventricular myocytes. The cells were loaded with the fluorescent indicator indo-1 in order to measure [Ca2+]i.
The application of caffeine to release calcium from the sarcoplasmic reticulum produced a rise of [Ca2+]i which decayed about 7-8 times more slowly than the electrically stimulated calcium transient. This suggests that the sarcoplasmic reticulum accounts for about 87% of the calcium removal. The rate of decay of the caffeine response was decreased to about 33% of the control by inhibiting the Na-Ca exchange with Ni2+. In the presence of Ni2+ the rate could be inhibited further by inhibiting either the sarcolemmal Ca-ATPase (by increasing extracellular calcium concentration, [Ca2+]o) or the mitochondria (with FCCP and oligomycin). The relative contributions of the various processes were estimated to be: sarcoplasmic reticulum 87%, mitochondria 1.7%, Na-Ca 8.7%, sarcolemmal Ca-ATPase 2.6%.
These experiments show that the Na-Ca exchange accounts for 67% of the calcium removal not mediated by the sarcoplasmic reticulum. This is a smaller fraction than in rabbit cardiac cells and highlights the importance of the Ca-ATPase in the rat heart.
旨在评估各种细胞内和肌膜系统对收缩期钙瞬变舒张的相对贡献。
实验在分离的大鼠心室肌细胞上进行。细胞加载荧光指示剂indo-1以测量[Ca2+]i。
应用咖啡因从肌浆网释放钙导致[Ca2+]i升高，其衰减速度比电刺激的钙瞬变慢约7-8倍。这表明肌浆网约占钙清除的87%。通过用Ni2+抑制钠钙交换，咖啡因反应的衰减速率降至对照的约33%。在存在Ni2+的情况下，通过抑制肌膜钙ATP酶（通过增加细胞外钙浓度，[Ca2+]o）或线粒体（用FCCP和寡霉素），速率可进一步受到抑制。估计各种过程的相对贡献为：肌浆网87%，线粒体1.7%，钠钙8.7%，肌膜钙ATP酶2.6%。
这些实验表明，钠钙交换占非由肌浆网介导的钙清除的67%。这一比例低于兔心肌细胞，突出了钙ATP酶在大鼠心脏中的重要性。
