Karjalainen A, Bygrave F L
Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra.
Biochem J. 1994 Jul 1;301 ( Pt 1)(Pt 1):187-92. doi: 10.1042/bj3010187.
A study was made of the initial responses of perfusate Ca2+ fluxes and bile flow to Ca(2+)-mobilizing agonists, following refinements to the methods for analysing these parameters in the perfused rat liver. Net Ca2+ efflux induced by vasopressin commences at 15 s, reaches a maximal rate at 35 s and declines to zero by 55 s, when Ca2+ influx commences. Vasopressin-induced increases in bile flow commence by 20 s, attain a maximal rate by 35 s and begin to decline at 50 s, to reach basal values by 90 s. Concomitant administration of glucagon modifies each of these actions of vasopressin in the following ways: it decreases by 5 s the time of onset of net Ca2+ efflux, and the time and magnitude of such efflux, and the time of onset of bile flow is decreased to 15 s, and the flow reaches maximal rates by 30 s. When the alpha 1-adrenergic agonist phenylephrine is used in place of vasopressin, Ca2+ efflux commences at 17-18 s and is greater in magnitude; little bile flow is induced by this agonist. Glucagon modifies the action of phenylephrine in the following ways: the onset of Ca2+ efflux is brought forward by 2-3 s, it is of lower magnitude and Ca2+ influx begins by 45 s; bile flow commences by 15-20 s, and reaches a maximum at 30 s, where the rate is much greater than in the absence of glucagon; this rate gradually declines to be near basal by 80 s. The onset of agonist-induced oxygen uptake was also brought forward by the co-administration of glucagon. Comparison of agonist-induced plasma-membrane Ca2+ fluxes and bile flow (with or without glucagon administration) suggests that correlations can be made between net Ca2+ fluxes and the transient increases seen in bile flow.
在对灌注大鼠肝脏中这些参数的分析方法进行改进之后，对灌注液Ca2+通量和胆汁流量对Ca(2+)动员激动剂的初始反应进行了研究。血管加压素诱导的净Ca2+外流在15秒开始，35秒达到最大速率，55秒时降至零，此时Ca2+内流开始。血管加压素诱导的胆汁流量增加在20秒开始，35秒达到最大速率，50秒开始下降，90秒时达到基础值。同时给予胰高血糖素会以以下方式改变血管加压素的这些作用：它使净Ca2+外流开始的时间提前5秒，以及这种外流的时间和幅度，胆汁流量开始的时间降至15秒，流量在30秒达到最大速率。当使用α1-肾上腺素能激动剂去氧肾上腺素代替血管加压素时，Ca2+外流在17 - 18秒开始且幅度更大；该激动剂几乎不诱导胆汁流动。胰高血糖素以以下方式改变去氧肾上腺素的作用：Ca2+外流的开始提前2 - 3秒，幅度较小且Ca2+内流在45秒开始；胆汁流量在15 - 20秒开始，30秒达到最大值，此时速率远高于未使用胰高血糖素时；该速率在80秒时逐渐下降至接近基础值。胰高血糖素的共同给药也使激动剂诱导的氧气摄取开始时间提前。激动剂诱导的质膜Ca2+通量与胆汁流量（无论是否给予胰高血糖素）的比较表明，净Ca2+通量与胆汁流量中观察到的短暂增加之间存在相关性。
