Friedman D B, Ordway G A, Williams R S
J Appl Physiol (1985). 1987 Apr;62(4):1721-3. doi: 10.1152/jappl.1987.62.4.1721.
To test the hypothesis that the high levels of endogenous catecholamines associated with strenuous exercise produce functional desensitization of cardiac beta-adrenergic receptors, we measured the bolus chronotropic dose of isoproterenol necessary to produce a 25-beats/min increase in heart rate (CD25) in the resting state and after the return of heart rate to resting levels after 60 min of treadmill running in 13 normal dogs. Immediately after exercise, 12 of 13 dogs were less sensitive to the chronotropic effects of beta-adrenergic receptor stimulation: mean CD25 increased from 1.16 +/- 0.17 to 3.50 +/- 0.98 micrograms (P less than 0.02). A similar reduction in isoproterenol sensitivity was evident regardless of whether testing was performed in the presence or absence of vagal blockade with atropine. By 3 h after exercise, CD25 had returned to the preexercise level, with no further change noted 24 h after exercise. There was no change in the CD25 when measured serially in three unexercised dogs. We conclude that a single bout of dynamic exercise is sufficient to produce a significantly decreased chronotropic responsiveness to isoproterenol. This phenomenon may represent an acute but transient desensitization of cardiac beta-adrenergic receptors.
为了验证与剧烈运动相关的内源性儿茶酚胺水平升高会导致心脏β - 肾上腺素能受体功能脱敏这一假说，我们测量了13只正常犬在静息状态下以及在跑步机上跑60分钟后心率恢复到静息水平时，使心率增加25次/分钟所需的异丙肾上腺素推注变时剂量（CD25）。运动后立即进行测量，13只犬中有12只对β - 肾上腺素能受体刺激的变时效应敏感性降低：平均CD25从1.16±0.17微克增加到3.50±0.98微克（P<0.02）。无论在有或无阿托品迷走神经阻滞的情况下进行测试，异丙肾上腺素敏感性均有类似降低。运动后3小时，CD25已恢复到运动前水平，运动后24小时未观察到进一步变化。对三只未运动的犬连续测量时，CD25没有变化。我们得出结论，单次动态运动足以使对异丙肾上腺素的变时反应性显著降低。这种现象可能代表心脏β - 肾上腺素能受体的急性但短暂的脱敏。
