Auld A M, Aspinall J, Barritt G J
Department of Biochemistry and Chemical Pathology, Flinders University School of Medicine, Bedford Park, South Australia.
Cardiovasc Res. 1987 Oct;21(10):772-8. doi: 10.1093/cvr/21.10.772.
The concentration of free calcium in the myoplasm of myocytes isolated from rat ventricles was measured using quin2. Incubation of myocytes with the acetoxymethylester of quin2 (50 mumol.litre-1) for 45 min was required to give effective loading with quin2. At 1 mmol.litre-1 extracellular calcium free calcium was 210(17) (n = 5) nmol.litre-1. Depolarisation of myocytes by addition of 40 mmol.litre-1 potassium caused a threefold increase in free calcium. Increases in extracellular calcium from 0.25 to 2.0 mmol.litre-1 caused a twofold increase in free calcium in polarised (resting) myocytes and a 2.5-fold increase in cells depolarised with potassium. The ability of verapamil to inhibit the electrically stimulated contraction of myocytes was dependent on the stimulation voltage. Half-maximal inhibition was given by 0.7 and 2 mumol.litre-1 verapamil at 50 and 100 V stimulation respectively. High concentrations of verapamil completely inhibited potassium induced increases in the fluorescence of quin2 loaded cells. Half-maximal inhibition was observed at 0.5 mumol.litre-1 verapamil. The calcium agonist CGP 28392 enhanced potassium induced fluorescence of quin2 loaded cells. Dibutyryl cyclic adenosine monophosphate and adrenaline increased the proportion of rod shaped cells that contracted in response to stimulation by low, but not high, voltage. Dibutyryl cyclic AMP caused a threefold increase in the potassium induced increase in free calcium. It is concluded that verapamil decreases and that calcium agonists, dibutyryl cyclic AMP, and increases in extracellular calcium increase free calcium, as monitored by intracellular quin2.
使用喹啉-2（quin2）测定从大鼠心室分离的心肌细胞肌浆中游离钙的浓度。需要将心肌细胞与喹啉-2的乙酰氧甲酯（50 μmol·L⁻¹）孵育45分钟，才能有效地加载喹啉-2。在1 mmol·L⁻¹的细胞外钙浓度下，游离钙为210(17)（n = 5）nmol·L⁻¹。加入40 mmol·L⁻¹钾使心肌细胞去极化，导致游离钙增加三倍。细胞外钙浓度从0.25 mmol·L⁻¹增加到2.0 mmol·L⁻¹，使极化（静息）心肌细胞中的游离钙增加两倍，在钾去极化的细胞中增加2.5倍。维拉帕米抑制心肌细胞电刺激收缩的能力取决于刺激电压。在50 V和100 V刺激下，分别给予0.7 μmol·L⁻¹和2 μmol·L⁻¹的维拉帕米可产生半数最大抑制作用。高浓度的维拉帕米完全抑制钾诱导的喹啉-2负载细胞荧光增加。在0.5 μmol·L⁻¹的维拉帕米浓度下观察到半数最大抑制作用。钙激动剂CGP 28392增强了钾诱导的喹啉-2负载细胞的荧光。二丁酰环磷腺苷和肾上腺素增加了对低电压而非高电压刺激有反应而收缩的杆状细胞的比例。二丁酰环磷腺苷使钾诱导的游离钙增加增加了三倍。结论是，如通过细胞内喹啉-2监测，维拉帕米降低游离钙，而钙激动剂、二丁酰环磷腺苷和细胞外钙增加则增加游离钙。
