Ahmed Z, Connor J A
Department of Physiology, State University of New York, Buffalo.
Cell Calcium. 1988 Apr;9(2):57-69. doi: 10.1016/0143-4160(88)90025-5.
The properties of Ca-regulation and -buffering of physiological levels of Ca-transients were examined in the soma of Archidoris monteryensis neurons. The rate of recovery from a Ca-transient was examined with two experimental protocols; in one the pulse duration was kept constant and its amplitude was varied, and in the other the duration was varied while the amplitude was kept constant. These experiments revealed that the recovery from a Ca-transient was approximately a first order process and the apparent first order rate constant was dependent on the duration of Ca-influx. The calcium buffer capacity of the cytoplasm was determined by an indirect method which utilised measured amounts of intracellular EGTA to reduce transient changes in free calcium. An equation for the cytoplasmic buffer capacity was derived on the assumption that the capacities of exogenous and endogenous Ca buffers summate linearly. The resting cytoplasmic Ca buffer capacity was 45.2 microM/delta pCa, when it was assumed that the incoming Ca diffuses a distance of 10 microns into the cytoplasm. For a diffusion distance of 5 microns it was 34.5 microM/delta pCa. In both cases, the buffer capacity increased with an increase in the size of Ca transient.
在蒙特雷阿氏海牛神经元的胞体中，研究了钙瞬变生理水平的钙调节和缓冲特性。采用两种实验方案研究了从钙瞬变恢复的速率；一种方案中，脉冲持续时间保持恒定，其幅度变化；另一种方案中，幅度保持恒定，持续时间变化。这些实验表明，从钙瞬变恢复大致是一个一级过程，表观一级速率常数取决于钙内流的持续时间。细胞质的钙缓冲能力通过一种间接方法测定，该方法利用测量的细胞内乙二醇双四乙酸（EGTA）量来减少游离钙的瞬时变化。基于外源和内源钙缓冲剂的能力线性叠加的假设，推导了细胞质缓冲能力的方程。当假设进入的钙扩散到细胞质中的距离为10微米时，静息细胞质钙缓冲能力为45.2微摩尔/ΔpCa。对于5微米的扩散距离，为34.5微摩尔/ΔpCa。在这两种情况下，缓冲能力都随着钙瞬变大小的增加而增加。
