Goetz T E, Manohar M
Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana-Champaign 61801.
Am J Vet Res. 1990 Jul;51(7):1008-11.
The effect of age on maximal heart rate induced by IV infusion of isoproterenol was studied in 19 healthy, sedentary, normothermic horses ranging in age from 0.25 to 9.90 years. Isoproterenol was administered IV (1.0 micrograms/kg of body weight/min) for 3 minutes, and the heart rate attained during the last 30 seconds of the infusion was determined. Linear regression of the maximal heart rate on age suggested that the rate decreased with age in a trend described by the equation: maximal heart rate (beats/min) = 209.63 - 3.28 x age (years). The regression coefficient (r) for this relation was 0.769 (P less than 0.001). These data indicate that as healthy horses age, their beta-adrenoceptor-mediated maximal chronotropic response is diminished.
在19匹年龄从0.25岁至9.90岁、健康、久坐、体温正常的马匹中，研究了年龄对静脉注射异丙肾上腺素诱导的最大心率的影响。以1.0微克/千克体重/分钟的速度静脉注射异丙肾上腺素3分钟，并测定输注最后30秒内达到的心率。最大心率与年龄的线性回归表明，心率随年龄下降，其趋势可用以下方程描述：最大心率（次/分钟）=209.63 - 3.28×年龄（岁）。该关系的回归系数（r）为0.769（P<0.001）。这些数据表明，随着健康马匹年龄的增长，其β-肾上腺素能受体介导的最大变时反应会减弱。
