Parker J C, Barritt G J, Wadsworth J C
Biochem J. 1983 Oct 15;216(1):51-62. doi: 10.1042/bj2160051.
The effects of adrenaline on 45Ca2+-exchange curves for isolated hepatocytes incubated under various steady-state conditions were investigated. Kinetic analysis showed that the simplest compartment configuration consistent with each set of data was a series configuration of a three-compartment closed system comprising compartment 1 (C1), the extracellular medium, and two kinetically distinct compartments of cellular exchangeable Ca2+, C2 and C3 (C1 = C2 = C3). Subcellular fractionation of hepatocytes labelled with 45Ca2+ at 0.1 mM-Ca2+ indicated that C3 includes exchangeable Ca2+ in the mitochondria and endoplasmic reticulum. The following results were obtained from experiments conducted at 37 degrees C at five different extracellular Ca2+ concentrations. For both untreated and adrenaline-treated cells, plots of the flux from C1 to C2 as a function of the extracellular Ca2+ concentration were best described by straight lines consistent with Ca2+ influx across the plasma membrane being a diffusion process. Adrenaline increased the value of the permeability constant for Ca2+ influx by 40%. For untreated cells, plots of the flux between C2 and C3 as a function of the concentrations of Ca2+ in these compartments approached a plateau at high Ca2+ concentrations. Adrenaline caused a 3-fold increase in the concentration of Ca2+ that gives half-maximal rate of Ca2+ transport from C2 to C3. At 1.3 mM extracellular Ca2+, a decrease in incubation temperature from 37 degrees C to 20 degrees C decreased the quantity of Ca2+ in C3 and the flux and fractional transfer rates for the transport of Ca2+ between C2 and C3. At 20 degrees C adrenaline increased the quantity of Ca2+ in C3 and the fractional transfer rates for the transfer of Ca2+ from C1 to C2, and from C2 to C3. At 37 degrees C and 2.4 mM extracellular Ca2+, antimycin A plus oligomycin decreased the quantity of Ca2+ in C3 and increased the fractional transfer rate for the transport of Ca2+ from C3 to C2. In the presence of antimycin A and oligomycin, adrenaline did not increase the quantity of Ca2+ in C2 or the flux and fractional transfer rate for the transport of Ca2+ from C1 to C2, whereas these parameters were increased in the absence of the inhibitors.
研究了肾上腺素对在各种稳态条件下孵育的离体肝细胞的45Ca2+交换曲线的影响。动力学分析表明，与每组数据一致的最简单的隔室构型是一个三室封闭系统的串联构型，该系统包括隔室1（C1），即细胞外介质，以及细胞内可交换Ca2+的两个动力学上不同的隔室C2和C3（C1 = C2 = C3）。用0.1 mM - Ca2+标记45Ca2+的肝细胞的亚细胞分级分离表明，C3包括线粒体和内质网中的可交换Ca2+。在37℃下于五种不同的细胞外Ca2+浓度进行实验，得到以下结果。对于未处理和肾上腺素处理的细胞，C1到C2的通量与细胞外Ca2+浓度的关系图最好用直线描述，这与跨质膜的Ca2+内流是一个扩散过程一致。肾上腺素使Ca2+内流的渗透常数增加了40%。对于未处理的细胞，C2和C3之间的通量与这些隔室中Ca2+浓度的关系图在高Ca2+浓度下接近平稳状态。肾上腺素使Ca2+从C2到C3运输达到最大速率一半时的Ca2+浓度增加了3倍。在细胞外Ca2+为1.3 mM时，孵育温度从37℃降至20℃会降低C3中的Ca2+量以及C2和C3之间Ca2+运输的通量和分数转运率。在20℃时，肾上腺素增加了C3中的Ca2+量以及Ca2+从C1到C2和从C2到C3转运的分数转运率。在37℃和细胞外Ca2+为2.4 mM时，抗霉素A加寡霉素降低了C3中的Ca2+量，并增加了Ca2+从C3到C2运输的分数转运率。在存在抗霉素A和寡霉素的情况下，肾上腺素不会增加C2中的Ca2+量或Ca2+从C1到C2运输的通量和分数转运率，而在没有抑制剂的情况下这些参数会增加。
