Effects of Catechin on Activity of Angiotensin-Converting Enzyme and Generation of Reactive Oxygen Species in Rat Aorta.

Activity of angiotensin-converting enzyme (ACE) and intensity of ROS generation in the aorta were studied in male Wistar rats intraperitoneally injected with a mixture of (+) and (-) stereoisomers of catechin. ACE activity in aortal segments was evaluated by hydrolysis of hippuryl-histidine-leucine; ROS generation was measured by oxidation of dichlorodihydrofluorescein. The dynamics of ACE activity and intensity of ROS generation in the aorta after catechin administration and their dependence on the catechin dose were studied. The effects of dihydroquercetin and fucoidin on the studied parameters were analyzed. Catechin increased ACE activity; the maximum increase was achieved in 3 h after administration. Catechin dose producing a half-maximum increase in ACE activity was 0.04 μg/kg. The effects of catechin on ACE activity was attenuated by dihydroquercetin and completely abolished by fucoidin. Catechin did not enhance ROS production in the aorta, and in a dose of 0.1 μg/kg even inhibited this process. It is hypothesized that isomers of catechin produce opposite effects on ROS generation in the aorta.