Angiotensin I Converting Enzyme (ACE) inhibitory activity and antihypertensive effects of grass carp peptides

In vitro and in vivo antihypertensive effects of grass carp peptides (GCP) were investigated. The amino acid composition and the angiotensinconverting enzyme inhibitory activity were evaluated using HPLC. GCP was administrated to spontaneously hypertensive rats (SHRs) and Wistar Kyoto rats (WKY) by single and long-term administration before blood pressure measurements. Plasma levels of angiotensin II (Ang II), rennin (RA), nitric oxide (NO), and plasma angiotensin I converting enzyme (ACE) activity were measured. The GCP molecular weight was between 725 and 1,228 Da with high levels of Leu, Asp, Phe, Gly, and Pro. The in vitro IC 50 value was 0.23 mg/mL. GCP lowered SHR blood pressure dose and timedependently. Little change occurred in WKY. The plasma level of Ang II and the ACE activity decreased. SHR RA and NO concentrations in plasma increased. The antihypertensive effect of GCP was associated with NO regulation and the rennin-angiotensin system.