Effects of bulb of Fritillaria ussuriensis maxim. on angiotensin converting enzyme and vascular release of NO/cGMP in rats.

The present study was designed to investigate whether the Bulbus Fritillaria shows a hypotensive effect via the angiotensin converting enzyme (ACE) inhibition and elicit NO/cGMP release in rat aortic rings. Intravenous injection of Bulbus Fritillaria water extract lowered the mean arterial pressure of anesthetized rats in a dose-dependent manner. The ACE activities were inhibited significantly by the additions of ethylacetate and butanol extracts from Bulbus Fritillaria, of which IC(50) values were 292 and 320 microg/ml, respectively. Moreover, angiotensin I-induced vasoconstriction was also strongly inhibited by the additions of ethylacetate and butanol extracts from Bulbus Fritillaria. In order to assess whether NO production was induced by Bulbus Fritillaria extracts, we directly measured NO and cGMP production levels from the aortic ring elicited by extracts of Bulbus Fritillaria. Our results showed that the hexane, butanol, and water extracts of Bulbus Fritillaria increased NO and cGMP productions in intact vascular tissue. These findings suggest that Bulbus Fritillaria extracts have a hypotensive effect in rats via the inhibition of ACE activity and direct release of NO/cGMP in the vascular tissue.