The Effect of Hydroalcoholic Extract of Olive Leaves on Blood Pressure in Rat Model of Two-Kidney, One-Clip Goldblatt Hypertension

Background: In Iran’s traditional medicine, the leaves of olive tree are of value for the treatment of hypertension. This study was designed to examine the effects of hydroalcoholic extract of olive leaves in rat model of two-kidney, one-clip hypertension and to further explore whether its hypotensive activity was mediated by enhancing the basal release of endothelium-derived nitric oxide.

Methods: Animals were divided into two main groups including sham-operated and renal artery-clipped ones. The latter was further divided into 5 groups of untreated rats, vehicle-treated rats, which received daily oral administrations of one ml distilled water, and extract-treated rats receiving olive leaves extract at 50, 150 or 500 mg/kg in the same volume of vehicle starting the next day after the operation. Four weeks later, mean blood pressure and heart rate were measured under anesthesia before and after the administration of NG-nitroL-arginine methyl ester (L-NAME).

Results: Mean arterial pressures, and right kidney and heart weights of untreated and vehicle-treated renal artery-clipped rats were significantly higher but left kidney weights were significantly lower than those of sham-operated animals. However, there was no significant difference between the heart rates of these groups. Compared to vehicle-treated renal artery-clipped rats, treatment with hydroalcoholic extracts of olive leaves at 50, 150 or 500 mg/kg/day was associated with significantly lower mean arterial pressure, right kidney and heart weights but did not affect heart rate or left kidney weights. The intravenous administration of L-NAME resulted in a significant increase in mean arterial pressure in sham-operated and extract-treated rats whereas there was no change in renal artery clipped or vehicle-treated groups.

Conclusion: The findings of the study show that hydroalcoholic extract of olive leaves prevents the clipinduced increase in mean arterial pressure, which might be partly mediated by enhancing the basal release of nitric oxide.