Grassi de Gende A O
Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, La Plata, Argentina.
J Mol Cell Cardiol. 1988 Dec;20(12):1087-93. doi: 10.1016/0022-2828(88)90589-5.
Net Ca2+ accumulation in vesicles of dog cardiac sarcoplasmic reticulum (CSR) was evaluated at three different pHs: 6.0, 6.8 and 7.6. The Ca2+ sequestration by CSR depends on Ca2+ concentration and on pH values. The curves that show the relationship between Ca2+ accumulated by CSR and external Ca2+ concentrations were shifted with pH changes, both in the absence and in the presence of potassium oxalate. Considering the curve at pH 6.8 as reference, a lower Ca concentration was needed to obtain the half-maximal value in Ca sequestration under pH 7.6 (0.04 +/- 0.006 and 0.79 +/- 0.09 microM at pH 7.6 and 6.8, respectively). Opposite results were obtained under pH 6.0 (13.66 +/- 1.29 microM). Net calcium release during active accumulation of Ca2+ and Ca2+ efflux from passively 45Ca2+ loaded CSR microsomes were significantly higher at alkaline pH than at acidic pH. The results suggest that in CSR alkaline pH would promote the increase in the rates of both, Ca2+ release and active Ca2+ accumulation, while opposite effects would be expected under acidic pH. Therefore, pH changes may regulate both, the Ca2+ level upon which the SR Ca2+ pump works (permeability effect) and the sequestration rate of the Ca2+ pump (variation in the affinity for calcium).
在三种不同的pH值（6.0、6.8和7.6）下，对犬心肌肌浆网（CSR）囊泡中的净Ca2+积累进行了评估。CSR对Ca2+的螯合作用取决于Ca2+浓度和pH值。在有无草酸钾的情况下，显示CSR积累的Ca2+与外部Ca2+浓度之间关系的曲线都随pH值变化而移动。以pH 6.8时的曲线为参考，在pH 7.6时获得Ca螯合半最大值所需的Ca浓度较低（pH 7.6和6.8时分别为0.04±0.006和0.79±0.09微摩尔）。在pH 6.0时得到相反的结果（13.66±1.29微摩尔）。在主动积累Ca2+过程中的净钙释放以及来自被动加载45Ca2+的CSR微粒体的Ca2+流出在碱性pH下显著高于酸性pH。结果表明，在CSR中，碱性pH会促进Ca2+释放速率和主动Ca2+积累速率的增加，而在酸性pH下预计会有相反的效果。因此，pH变化可能会调节SR Ca2+泵工作的Ca2+水平（通透性效应）以及Ca2+泵的螯合速率（对钙亲和力的变化）。
