Purpose: To investigate the blood pressure-lowering effect of green tea (GT) extract alone and in combination with an angiotensin converting enzyme (ACE) inhibitor, perindopril, on rats.
Methods: The study consisted of four groups of five spontaneously hypertensive rats (SHR): negative control (2 % tragacanth mucilage), positive control group (perindopril, 0.36 mg/kg/day) and two treatment groups (green tea, 25 mg/kg/day; and combined green tea/perindopril). The treatments were given orally for 14 days. Systolic blood pressure was measured before and after treatment using the tail cuff technique. Angiotensin converting enzyme activity in the lung homogenate of the hypertensive rats was determined spectrophotometrically.
Results: Green tea extract significantly reduced the rats’ systolic blood pressure (p < 0.05) but did not inhibit the angiotensin-converting enzyme. The combination of green tea extract with perindopril also caused a significant decline in blood pressure (p < 0.001). However, the green tea extract attenuated the inhibition of the angiotensin-converting enzyme activity by perindopril.
Conclusion: Green tea extract produces anti-hypertensive activity in rats, but its mechanism of action is not via inhibition of angiotensin-converting enzyme. The interaction of GT extract with perindopril results in a reduction of ACE inhibitory activity.
Effects on Plasma Angiotensin-Converting Enzyme Activity and Circulating Renin of Lisinopril and Enalapril Alone and in Combination with Propranolol in Healthy Volunteers
