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Effects of protocatechuic acid on endothelium‐dependent vascular function and superoxide level in hypertensive rats

Oxidative stress has been recognized as an important factor for the pathogenesis of hypertension. Recently, protocatechuic acid (PCA; 3,4‐dihydroxybenzoic acid), a simple phenolic acid, has been found to be a strong antioxidant. In this study, we investigated the effects of PCA on endothelium‐dependent vascular function and superoxide level in spontaneously hypertensive rats (SHR). The SHR were randomly divided into SHR with PCA supplement (SHR+PCA) and without supplement (SHR) groups. Wistar‐Kyoto (WKY) rats were used as the normotensive control group. The SHR+PCA group was supplemented with PCA adjusted from their daily water consumption for 8 weeks. Rat thoracic aortas were isolated for the measurement of endothelium‐dependent and endothelium‐independent vasorelaxant responses in the organ baths. The serum levels of superoxide dismutase (SOD) and thiobarbituric acid reactive substance (TBARS) were also evaluated. We found that the endothelium‐dependent vasorelaxant responses to acetylcholine were significantly (p<0.05) decreased in the SHR compared with the WKY. The PCA supplement significantly (p<0.05) ameliorated the endothelium‐dependent vasorelaxation. However, there was no significant difference in the endothelium‐independent vasorelaxation among three groups. Moreover, the PCA supplement tended to increase the SOD levels, but not TBARS level. We suggested that the PCA supplement could improve the endothelium‐dependent vascular dysfunction induced by hypertension.