ORAL-ADMINISTRATION OF PEPTIDES DERIVED FROM BONITO BOWELS DECREASES BLOOD-PRESSURE IN SPONTANEOUSLY HYPERTENSIVE RATS BY INHIBITING ANGIOTENSIN-CONVERTING ENZYME

1. Peptides C111 (Gly-Val-Tyr-Pro-His-Lys) and C112 (Ile-Arg-Pro-Val-Gln), extracted from the autolysis product of bonito liver and intestine, have been shown to inhibit angiotensin converting enzyme (ACE) activity in vitro with IC50s of 1.6 mu M and 1.4 mu M, respectively. We examined the effects of oral administration of these peptides on blood pressure. 2. Oral administration of these peptides (500 mg kg- 1 body weight each) inhibited the pressor effect of intravenously administered angiotensin I in Sprague-Dawley rats. 3. In spontaneously hypertensive rats, oral administration of these peptides (100-200 mg kg-1 body weight) showed depressor effects. 4. These results suggest that the peptides, C 111 and C 112, are orally effective ACE inhibitors with hypotensive effect.