Cardiovascular effects ofArbutus unedo L. in spontaneously hypertensive rats

In order to examine the effect of Arbutus unedo extract on the development of genetic hypertension, three groups of six male spontaneously hypertensive rats (SHR) from 4 to 10 weeks of age, received orally an aqueous extract of the root of this Ericaceae plant at doses of 5, 50 and 250 mg/kg/24 h. The fourth group (n = 6) received tap water only and served as a control. A significant (p < 0.01) reduction of indirect systolic blood pressure (BP) was observed after 4 weeks of treatment with the two highest doses but this effect attenuated 2 weeks later. The continuous measurement of direct BP in conscious 10-week-old rats indicated that chronic treatment with Arbutus did not significantly alter the BP level, the heart rate (HR), the cardiac baroreflex sensitivity and the sympathetic nervous and renin– angiotensin system activities. In contrast, Arbutus (50 mg/kg/24 h) attenuated the pressor responses to phenylephrine and angiotensin I. Finally, a diuretic effect was evidenced in the group receiving the highest dose. It is concluded that chronic oral administration of Arbutus unedo slowly delayed the development of hypertension but did not alter the final level of BP and HR in the SHR. The vascular and renal effects of this plant, which may account for its use in folk medicine, require a more detailed analysis.