Carotid baroreflex responsiveness in normotensive African Americans is attenuated at rest and during dynamic leg exercise
Carotid baroreflex responsiveness in normotensive African Americans is attenuated at rest and during dynamic leg exercise
复制标题
血压正常的非洲裔美国人的颈动脉压力反射反应在休息和动态腿部运动期间减弱
作者：
Seth W. Holwerda;M. Samels;D. Keller
有证据表明，非洲裔美国人（AAs）和高加索美国人（CA）之间的差异，心血管反应的生理应激。本研究验证了这样一个假设，即在运动过程中，与CA相比，AA中颈动脉压力感受性反射（CBR）对心率（HR）和血压的控制降低。在23名非高血压男性受试者（12名AA; 11名CA;年龄19-26岁）中，连续记录静息时和腿部骑车期间的平均动脉压（MAP）和HR。通过5秒脉冲颈部压力（NP，模拟低血压）和颈部抽吸（NS，模拟高血压）（范围为+45至−80 Torr）评估CBR对HR和MAP的控制。在所有NS刺激（−20、−40、−60、−80 Torr）下，AA组表现出减弱的CBR介导的HR（AA，−8.9 ± 1.9 vs CA，−14.1 ± 2.3 bpm; P < 0.001）和MAP（AA，−6.4 ± 1 vs CA，−7.8 ± 0.8 mmHg; P < 0.05）降低。尽管在模拟的刺激反应曲线中观察到类似的增益和重置幅度，但运动期间AA对NS的HR（AA，−8.2 ± 1.6 vs. CA，−11.8 ± 3 bpm; P < 0.05）和MAP（AA，−6.8 ± 0.9 vs. CA，−8.2 ± 1.1 mmHg; P < 0.05）反应持续衰减。在静息或运动时，两组之间未检测到CBR介导的HR和MAP对NP的反应存在差异。这些数据表明，在稳态运动过程中，与CA对应物相比，AA防御高血压挑战的能力受损。
Evidence suggests differences between African Americans (AAs) and Caucasian Americans (CAs) in cardiovascular responsiveness to physiological stressors. This study tested the hypothesis that carotid baroreflex (CBR) control of heart rate (HR) and blood pressure is reduced in AAs compared to CAs during exercise. Mean arterial pressure (MAP) and HR were continuously recorded at rest and during leg cycling in 23 non-hypertensive male subjects (12 AA; 11 CA; age 19–26 years). CBR control of HR and MAP was assessed with 5-s pulses of neck pressure (NP, simulated hypotension) and neck suction (NS, simulated hypertension) ranging from +45 to −80 Torr. Across all NS stimuli (−20, −40, −60, −80 Torr) at rest, the AA group demonstrated attenuated CBR-mediated reductions in HR (AA, −8.9 ± 1.9 vs. CA, −14.1 ± 2.3 bpm; P < 0.001) and MAP (AA, −6.4 ± 1 vs. CA, −7.8 ± 0.8 mmHg; P < 0.05). Despite similar gain and magnitude of resetting observed in the modeled stimulus response curves, an attenuation among AAs persisted in HR (AA, −8.2 ± 1.6 vs. CA, −11.8 ± 3 bpm; P < 0.05) and MAP (AA, −6.8 ± 0.9 vs. CA, −8.2 ± 1.1 mmHg; P < 0.05) responses to NS during exercise. No differences in CBR-mediated HR and MAP responses to NP were detected between groups at rest or during exercise. These data suggest impairment in the ability to defend against a hypertensive challenge among AAs during steady-state exercise compared to their CA counterparts.
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