Seifen E, Kennedy R H
Eur J Pharmacol. 1986 Aug 15;127(3):233-8. doi: 10.1016/0014-2999(86)90369-9.
The positive chronotropic effects of the dihydropyridine calcium agonist BAY K-8644 and calcium were studied in spontaneously beating right guinea-pig atria. Within the temperature range from 22 to 37 degrees C, the following observations were made: (1) The basal pacemaker frequency increased linearly with the ambient temperature; (2) the increase in pacemaker rate produced by a maximally effective concentration of BAY K-8644 was of the same magnitude as that produced by calcium; (3) the increases in pacemaker rate produced by BAY K-8644 and by calcium were directly proportional to the increase in temperature above 22 degrees C; and (4) at 37 degrees C, the apparent ED50 for the positive chronotropic effect of calcium was 2.3 X 10(-3) M and of BAY K-8644 was 0.7 X 10(-7) M. At temperatures below 22 degrees C, irregular pacemaking activity or complete arrest of pacemaking activity frequently occurred. The data are in strong support of the assumption that BAY K-8644 elicits its positive chronotropic effect by increasing the availability of calcium ions.
在豚鼠右心房自搏标本上研究了二氢吡啶类钙激动剂BAY K - 8644和钙的正性变时作用。在22至37摄氏度的温度范围内，有以下发现：（1）基础起搏频率随环境温度呈线性增加；（2）最大有效浓度的BAY K - 8644所产生的起搏频率增加幅度与钙所产生的相同；（3）BAY K - 8644和钙所产生的起搏频率增加与22摄氏度以上的温度升高成正比；（4）在37摄氏度时，钙正性变时作用的表观ED50为2.3×10⁻³ M，BAY K - 8644的表观ED50为0.7×10⁻⁷ M。在低于22摄氏度时，常出现不规则起搏活动或起搏活动完全停止。这些数据有力支持了BAY K - 8644通过增加钙离子的可用性而产生正性变时作用这一假设。
