Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
Math Biosci. 1981 Apr;53(3-4):275-310. doi: 10.1016/0025-5564(81)90022-5.
A model is proposed to describe the Na-Ca exchange in excitable tissues. The present scheme requires a carrier mechanism that exchanges 3Na for 1Ca across the membrane under the electrochemical gradient of Na. The carriers, assumed to be trivalent anions, have monovalent and divalent sites; Ca and Na can compete only at the second site. The partially and fully loaded carrier-ion complexes are mobile and diffusible across the membrane. Subsequently, analytical expressions for Na and Ca unidirectional flux at steady state are derived in terms of intracellular concentration (Na(i) and Ca(i)) and extracellular concentration (Na(o) and Ca(o)) as well as membrane potential, E(M). Published experimental flux data on cardiac muscle, squid axon, and rat synaptosomes can be satisfactorily fitted with the flux equation simply by adjusting the numerical constants.
提出了一个模型来描述兴奋组织中的 Na-Ca 交换。该方案要求载体机制在 Na 的电化学梯度下跨膜交换 3Na 对 1Ca。载体被假设为三价阴离子,具有单价和二价位点;Ca 和 Na 只能在第二个位点竞争。部分和完全加载的载体离子复合物是可移动和可扩散穿过膜的。随后,根据细胞内浓度(Na(i) 和 Ca(i))和细胞外浓度(Na(o) 和 Ca(o))以及膜电位 E(M),推导出了稳态下 Na 和 Ca 单向通量的解析表达式。简单地通过调整数值常数,就可以用通量方程很好地拟合心脏肌肉、鱿鱼轴突和大鼠突触体的已发表实验通量数据。