Farah Vera de Moura Azevedo, De Angelis Kátia, Joaquim Luis Fernando, Candido Georgia O, Bernardes Nathalia, Fazan Rubens, Schaan Beatriz D'Agord, Irigoyen Maria-Claudia
Hypertension Unit, Heart Institute, University of Sao Paulo, Medical School, Sao Paulo, Brazil.
Clinics (Sao Paulo). 2007 Aug;62(4):477-82. doi: 10.1590/s1807-59322007000400015.
The aim of the present study was to evaluate the autonomic modulation of the cardiovascular system in streptozotocin (STZ)-induced diabetic spontaneously hypertensive rats (SHR), evaluating baroreflex sensitivity and arterial pressure and heart rate variability.
Male SHR were divided in control (SHR) and diabetic (SHR+DM, 5 days after STZ) groups. Arterial pressure (AP) and baroreflex sensitivity (evaluated by tachycardic and bradycardic responses to changes in AP) were monitored. Autoregressive spectral estimation was performed for systolic AP (SAP) and pulse interval (PI) with oscillatory components quantified as low (LF:0.2-0.6Hz) and high (HF:0.6-3.0Hz) frequency ranges.
Mean AP and heart rate in SHR+DM (131+/-3 mmHg and 276+/-6 bpm) were lower than in SHR (160+/-7 mmHg and 330+/-8 bpm). Baroreflex bradycardia was lower in SHR+DM as compared to SHR (0.55+/-0.1 vs. 0.97+/-0.1 bpm/mmHg). Overall SAP variability in the time domain (standard deviation of beat-by-beat time series of SAP) was lower in SHR+DM (3.1+/-0.2 mmHg) than in SHR (5.7+/-0.6 mmHg). The standard deviation of the PI was similar between groups. Diabetes reduced the LF of SAP (3.3+/-0.8 vs. 28.7+/-7.6 mmHg2 in SHR), while HF of SAP were unchanged. The power of oscillatory components of PI did not differ between groups.
These results show that the association of hypertension and diabetes causes an impairment of the peripheral cardiovascular sympathetic modulation that could be, at least in part, responsible for the reduction in AP levels. Moreover, this study demonstrates that diabetes might actually impair the reduced buffer function of the baroreceptors while reducing blood pressure.
本研究旨在评估链脲佐菌素（STZ）诱导的糖尿病自发性高血压大鼠（SHR）心血管系统的自主神经调节，评估压力反射敏感性以及动脉血压和心率变异性。
雄性SHR分为对照组（SHR）和糖尿病组（SHR+DM，STZ注射后5天）。监测动脉血压（AP）和压力反射敏感性（通过对AP变化的心动过速和心动过缓反应进行评估）。对收缩压AP（SAP）和脉搏间期（PI）进行自回归谱估计，振荡成分量化为低频（LF：0.2 - 0.6Hz）和高频（HF：0.6 - 3.0Hz）范围。
SHR+DM组的平均AP和心率（131±3 mmHg和276±6次/分钟）低于SHR组（160±7 mmHg和330±8次/分钟）。与SHR相比，SHR+DM组的压力反射性心动过缓更低（0.55±0.1对0.97±0.1次/分钟/mmHg）。SHR+DM组SAP在时域的总体变异性（逐搏时间序列的标准差）低于SHR组（3.1±0.2 mmHg对5.7±0.6 mmHg）。两组间PI的标准差相似。糖尿病降低了SAP的LF（SHR中为3.3±0.8对28.7±7.6 mmHg²），而SAP的HF未改变。两组间PI的振荡成分功率无差异。
这些结果表明，高血压与糖尿病的关联导致外周心血管交感神经调节受损，这可能至少部分是AP水平降低的原因。此外，本研究表明，糖尿病在降低血压的同时，实际上可能损害压力感受器降低的缓冲功能。
