2005 Volume 69 Issue 5 Pages 911-915
In order to elucidate the mechanism of the antihypertensive action of dried bonito (katsuobushi), we compared the effects of dried bonito extracts with those of captopril, an angiotensin I-converting enzyme (ACE) inhibitor, on aorta preparations isolated from rats. Dried bonito extracts (3×10−4 to 3×10−3 g/ml) more potently relaxed contractions induced by norepinephrine (10−7 M) than contractions induced by KCl (55.9 mM). Dried bonito extracts (3×10−3 g/ml) slightly inhibited 10−7 M angiotensin I-induced contractions. In contrast, captopril (10−8 to 10−7 M) did not affect 10−7 M norepinephrine- or 55.9 mM KCl-induced contractions, but a higher concentration of captopril (10−6 M) very slightly relaxed it. Captopril (10−8 to 10−6 M) markedly inhibited 10−7 M angiotensin I-induced contractions in a concentration-dependent manner. These results suggest that antihypertensive mechanism of action induced by dried bonito involves direct action on vascular smooth muscle in addition to ACE-inhibitory activity.
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