Le Blanc P R, Rakusan K
Can J Cardiol. 1987 Jun-Aug;3(5):246-50.
Heart rate, stroke volume, cardiac output, its distribution and organ blood flows were measured, using the microsphere technique (15 micron in diameter microspheres), in 5, 12 and 24 months old conscious male rats. Each rat was then infused with isoproterenol (0.2 microgram/kg.min) and the measurements were repeated. It was found that resting cardiovascular values do not change within the age range studied, with the exception of the renal blood flow. After infusion of isoproterenol, the heart rate and cardiac output increased in the youngest group while only smaller increase in heart rate and no significant changes in cardiac output were found in the oldest group. Similarly, organ blood flow increased after isoproterenol in all organs studied in the 5 months group, with significance levels reached in the case of blood supply to the right and left ventricles, total heart, skin and carcass. In contrast, infusion of the same dose of isoproterenol in the 24 months old animals did not elicit any significant changes in the regional blood flow. Thus, the response to beta-adrenergic stimulation is depressed with advancing age. This finding of decreased in vivo response to beta-adrenergic stimulation may be a mechanism for the altered cardiovascular performance during stress seen in aged animals and man.
采用微球技术（直径15微米的微球），对5、12和24月龄的雄性清醒大鼠测量心率、每搏输出量、心输出量、其分布及器官血流量。随后给每只大鼠输注异丙肾上腺素（0.2微克/千克·分钟），并重复上述测量。结果发现，在所研究的年龄范围内，除肾血流量外，静息心血管值无变化。输注异丙肾上腺素后，最年幼组的心率和心输出量增加，而最年长组仅心率有较小增加，心输出量无显著变化。同样，5月龄组所有研究器官在输注异丙肾上腺素后器官血流量均增加，右心室、左心室、全心、皮肤和躯体的供血情况达到显著水平。相比之下，给24月龄动物输注相同剂量的异丙肾上腺素未引起局部血流量的任何显著变化。因此，随着年龄增长，对β-肾上腺素能刺激的反应减弱。这一在体对β-肾上腺素能刺激反应降低的发现可能是老年动物和人类在应激期间心血管功能改变的一种机制。
