Abstract
The renin-angiotensin (RA) system is considered to be one of the important factors involved in essential hypertension. Peptides with a molecular weight of 1, 000-2, 000, previously obtained by enzymatic hydrolysis of sardine muscle, have been shown to have in vitro angiotensin I-converting enzyme (ACE) -inhibitory activity. In the present experiment, the blood pressure-reduction and vasodilatory effects of these peptides in vivo were examined. A blood pressure reduction test using SHR rats showed a cleady recognizable effect as a result of intravenous administration. Furthermore, when the peptides (dosages: 0.5, 1.0, 2.0 and 4.0g/kg) were orally administered in 30% vitellinic solution, the blood pressure reduction showed a dose-dependent increase. The rate of reduction increased for about 3h and this effect still continued even beyond 6h after administration. When peptide samples (dosages: 2, 4, 8 and 16g/animal) were orally administered to rabbits, dilation of the aural blood vessels was observed 20min after administration. Even at 120min after peptide administration, persistent vasodilation was observed.
