Effect of Atenolol or Nebivolol Administration on Blood Pressure Variability and its Impact on White Organ Damage in Spontaneously Hypertensive Rats

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Abstract

Background: Hypertension-related cardiovascular risk has been traditionally considered the result of sustained blood pressure elevation, leading to target organ injury. In recent years, other factors have been described, such as blood pressure and central blood pressure variability, also directly affecting target organ injury.

Objective: The aim of this study was to assess the effects of chronic atenolol or nebivolol administration on short-term blood pressure variability and target organ injury at the left ventricular and aortic level.

Method: Spontaneously hypertensive rats (SHR) were treated for 8 weeks with a single daily dose of atenolol, nebivolol or vehicle.Blood pressure and its short-term variability were measured and echocardiography was performed. The left ventricle and thoracic aorta were removed to quantify the expression of transforming growth factor β and to perform histological studies.

Results: Chronic treatment with nebivolol reduced mean arterial pressure (MAP) and its variability to a greater extent than atenolol(MAP: WKY:118.6±8.0 mmHg, SHR: 174.6±2.1 mmHg a; SHR-atenolol: 155.2 ± 2.1 mmHg a, b, SHR-nebivolol: 122.3±2.3 mmHg b, c , MAP variability: WKY: 3.8±0.2 mmHg; SHR: 6.2±0.3 mmHg a; SHR-atenolol: 5.2±0.3 mmHg a, b; SHR-nebivolol: 4.2±0.2 mmHg b, c; a p<0.05 vs. WKY rats; b p<0.05 vs. SHR; c p<0.05 vs. SHR-atenolol).

Conclusions: The analysis of target organ injury showed that nebivolol reduced the content of ventricular fibrosis, decreased aortic media thickness and induced greater reduction of transforming growth factor β overexpression in both organs compared to SHR treated with vehicle or atenolol. These findings suggest that a greater reduction in central blood pressure, together with a decrease in blood pressure variability, would contribute to the better protection of target organ injury with nebivolol than with atenolol.