Effects of extracts of Radix Scrophulariae on blood pressure in spontaneously hypertensive rats and the underlying mechanisms

Abstract

To explore the effects of extracts of Radix Scrophulariae (ERS) on blood pressure, vasoconstrictors and morphology of artery in spontaneously hypertensive rats (SHRs). Fifty SHRs were randomly divided into SHR, SHR plus 40 mg/kg of captopril, SHR plus 70 mg/kg of ERS, SHR plus 140 mg/kg of ERS and SHR plus 280 mg/kg of ERS groups. Wistar-Kyoto (WKY) rats were randomly divided into two groups, namely, WKY and WKY plus 140 mg/kg of ERS groups. The rats were orally administered with the corresponding drugs or drinking water once a day for 20 weeks. The blood pressure was determined every three weeks. At the 21st week, the concentrations of noradrenaline (NA), angiotensin II (Ang II), thromboxane B(2) (TXB(2)) and 6-keto-prostaglandin F(1α) in serum and endothelin-1 (ET-1) were detected by enzyme-linked immunosorbent assay. The morphological changes in abdominal aorta were observed under an optical microscope with hematoxylin and eosin staining. The ratio of intima-media thickness/lumen radius of abdominal aorta was calculated. ERS significantly lowered the blood pressure of SHRs from the 3rd to the 21st week; ERS also reduced the levels of NA, Ang II, ET-1 and TXB(2), decreased the intima-media thickness of abdominal aortal wall and improved the morphological changes in abdominal aorta in SHRs. In addition, ERS did not significantly change blood pressure and vasoactive substances in WKY rats. ERS possesses beneficial effects in inhibiting hypertension and attenuating arteriosclerosis. The underlying mechanism may be associated with restraining the release of vasoconstrictors, such as NA, Ang II, ET-1 and TXB(2).