Hopkins M G, Spina R J, Ehsani A A
Section of Applied Physiology, and Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Appl Physiol (1985). 1996 Feb;80(2):516-21. doi: 10.1152/jappl.1996.80.2.516.
To determine whether the adaptive increase in left ventricular systolic function in the trained state is mediated by enhanced responses to beta-adrenergic stimulation, we studied eight male endurance athletes [age 27 +/- 1.8 yr; maximal O2 uptake (VO2max) 60 +/- 0.9 (SE) ml x kg-1 x min-1] and eight sedentary men (age 27 +/- 1.4 yr; VO2max 43.1 +/- 1.7 ml x kg-1 x min-1). Left ventricular function was evaluated with two-dimensional echocardiography and pulsed Doppler transmitral flow velocity profile in the basal state, after parasympathetic blockade by atropine, and during infusion of dobutamine. Cardiac output and stroke volume, determined with the acetylene rebreathing technique, during maximal exercise were significantly higher in the endurance athletes than in the sedentary men (28.9 +/- 1.7 vs. 23 +/- 1.23 1/min, P = 0.019, and 162 +/- 12 vs. 125 +/- 7 ml/min, P = 0.029). Endurance athletes showed physiological volume overload-left ventricular hypertrophy and greater enhancements of left ventricular systolic function and filling dynamics in response to dobutamine than did the sedentary men as reflected in 1) a steeper slope of the fractional shortening-end-systolic wall stress relationship (-0.986 +/- 0.16 vs. -0.508 +/- 0.054, P = 0.014, athletes vs. controls) and 2) a higher early-to-late transmitral diastolic Doppler velocity ratio (2.14 +/- 0.14 vs. 1.74 +/- 0.12, P = 0.016) at a comparable heart rate. Although endurance athletes had a significantly greater inotropic response to dobutamine, they demonstrated a markedly attenuated chronotropic response to beta1-adrenergic stimulation compared with sedentary subjects. Our findings suggest that, even with a blunted chronotropic response, endurance-trained young men show an augmented inotropic response to a beta1-adrenergic agonist that, along with physiological volume overload hypertrophy and increased diastolic filling, can contribute to a larger stroke volume during maximal exercise in the trained state.
为了确定训练状态下左心室收缩功能的适应性增强是否由对β-肾上腺素能刺激的反应增强介导，我们研究了8名男性耐力运动员[年龄27±1.8岁；最大摄氧量(VO2max)60±0.9(标准误)ml·kg-1·min-1]和8名久坐不动的男性(年龄27±1.4岁；VO2max 43.1±1.7 ml·kg-1·min-1)。在基础状态、用阿托品阻断副交感神经后以及多巴酚丁胺输注期间，用二维超声心动图和脉冲多普勒二尖瓣血流速度曲线评估左心室功能。用乙炔再呼吸技术测定的耐力运动员在最大运动时的心输出量和每搏量显著高于久坐不动的男性(28.9±1.7 vs.23±1.23 l/min，P = 0.019，以及162±12 vs.125±7 ml/min，P = 0.029)。耐力运动员表现出生理性容量超负荷-左心室肥厚，并且与久坐不动的男性相比，对多巴酚丁胺的反应中左心室收缩功能和充盈动力学有更大增强，这体现在1) 缩短分数-收缩末期壁应力关系的斜率更陡(-0.986±0.16 vs.-0.508±0.054，P = 0.014，运动员与对照组)，以及2) 在相当的心率下二尖瓣舒张期多普勒早期与晚期速度比值更高(2.14±0.14 vs.1.74±0.12，P = 0.016)。尽管耐力运动员对多巴酚丁胺有显著更大的变力反应，但与久坐不动的受试者相比，他们对β1-肾上腺素能刺激的变时反应明显减弱。我们的研究结果表明，即使变时反应减弱，耐力训练的年轻男性对β1-肾上腺素能激动剂表现出增强的变力反应，这与生理性容量超负荷肥厚和舒张期充盈增加一起，可导致训练状态下最大运动时更大的每搏量。
