Lapointe D S, Olson M S
Department of Biochemistry, University of Texas Health Science Center, San Antonio.
Cell Calcium. 1991 Nov;12(10):743-53. doi: 10.1016/0143-4160(91)90043-e.
The kinetics of calcium movements in the isolated perfused rat liver were examined using compartmental analysis of the efflux profiles of 45Ca2+ from 45Ca(2+)-equilibrated livers under a variety of calcium concentrations and hormonal treatments. From the 45Ca2+ efflux profiles, we determined that a three compartment model was appropriate to describe the movements of calcium in the liver on the time scale of the experiments. Hormonal treatment with the alpha-adrenergic agonist, phenylephrine, or the vasoactive peptide, vasopressin, during the efflux period lowered significantly the rate of transfer of Ca2+ between the internal compartments at all of the calcium concentrations employed. Also, phenylephrine treatment leads to increased transfer of Ca2+ into the liver from the perfusate. The temporal characteristics of the phenylephrine and vasopressin sensitive Ca2+ pools were examined by pulsing livers, loaded for variable periods of time with 45Ca2+, with the two hormones during the efflux of 45Ca2+ to measure the kinetics of Ca2+ exchange in the hormone-sensitive pools. Results from these experiments indicate that the rate of unstimulated Ca2+ efflux, k2, for the phenylephrine and vasopressin sensitive Ca2+ pools, modeled as a one compartment system, are the same, 0.074 and 0.078 min-1 for phenylephrine and vasopressin respectively, corresponding to half times for turnover of the pool(s) of 9.3 and 8.9 min, respectively.
利用隔室分析法，在多种钙浓度和激素处理条件下，研究了45Ca(2+)平衡的离体灌注大鼠肝脏中45Ca2+流出曲线，以此来检测钙运动的动力学。根据45Ca2+流出曲线，我们确定三室模型适用于描述实验时间尺度上肝脏中钙的运动。在流出期，用α-肾上腺素能激动剂去氧肾上腺素或血管活性肽血管加压素进行激素处理，在所有使用的钙浓度下，均显著降低了内部隔室之间Ca2+的转移速率。此外去氧肾上腺素处理导致灌流液中Ca2+向肝脏的转移增加。通过对用45Ca2+加载不同时间的肝脏进行脉冲处理，并在45Ca2+流出期间用这两种激素来检测去氧肾上腺素和血管加压素敏感的Ca2+池的时间特性，以测量激素敏感池中Ca2+交换的动力学。这些实验结果表明，对于去氧肾上腺素和血管加压素敏感的Ca2+池，若将其模拟为单室系统，未受刺激的Ca2+流出速率k2是相同的，去氧肾上腺素和血管加压素分别为0.074和0.078 min-1，分别对应池周转的半衰期为9.3和8.9分钟。
