CARDIOVASCULAR EFFECTS OF ARBUTUS-UNEDO-L. IN SPONTANEOUSLY HYPERTENSIVE RATS

In order to examine the effect of Arbutus unedo extract on the develop ment of genetic hypertension, three groups of six male spontaneously h ypertensive rats (SHR) from 4 to 10 weeks of age, received orally an a queous extract of the root of this Ericaceae plant at doses of 5, 50 a nd 250 mg/kg/24 h. The fourth group (n = 6) received tap water only an d served as a control. A significant (p < 0.01) reduction of indirect systolic blood pressure (BP) was observed after 4 weeks of treatment w ith the two highest doses but this effect attenuated 2 weeks later. Th e continuous measurement of direct BP in conscious 10-week-old rats in dicated that chronic treatment with Arbutus did not significantly alte r the BP level, the heart rate (HR), the cardiac baroreflex sensitivit y and the sympathetic nervous and renin-angiotensin system activities. In contrast, Arbutus (50 mg/kg/24 h) attenuated the presser responses to phenylephrine and angiotensin I. Finally, a diuretic effect was ev idenced in the group receiving the highest dose. It is concluded that chronic oral administration of Arbutus unedo slowly delayed the develo pment of hypertension but did not alter the final level of BP and HR i n the SHR. The vascular and renal effects of this plant, which may acc ount for its use in folk medicine, require a more detailed analysis. ( C) 1998 John Wiley & Sons, Ltd.