The influence of dietary peptide inhibitors of angiotensin-converting enzyme on the hypotensive effects of enalapril

BACKGROUND Enalapril is an antihypertensive medicine that inhibits angiotensin I-converting enzyme (ACE). The present study investigated interactions between enalapril and a fermented milk product (FMP) containing the ACE-inhibitory peptides, Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP). METHODS Single-dose and long-term (6-week) in vivo studies were used to investigate the effects of enalapril and FMP on blood pressure in spontaneously hypertensive rats. RESULTS Single-dose oral administration of concomitant enalapril and FMP (VPP, IPP: 3.5 mg/kg) produced a lower antihypertensive effect than enalapril monotherapy. However, this effect was not observed in animals administered a lower dose of FMP (VPP, IPP: 1.75 mg/kg) along with enalapril. In rats administered enalapril concomitantly with a fish protein product (FPP) containing a different ACE inhibitory peptide (Leu-Lys-Pro-Asn-Met), significant attenuation of the antihypertensive effect was also observed 1 and 2 h after administration, as compared to enalapril monotherapy. During a 6-week oral administration study, the enalapril monotherapy group showed significant antihypertensive effects compared to those observed in the controls on day 28. Oral administration of enalapril and FMP, with a 1-h interval between doses, resulted in significant antihypertensive effects on day 35, indicating a delayed onset in comparison to enalapril monotherapy. In rats receiving enalapril monotherapy for 28 days, followed by 14 days of concomitant FMP, significant antihypertensive effects were observed after day 35, and these did not differ significantly from the effects observed during enalapril monotherapy. CONCLUSIONS The present findings suggested that long-term concomitant intake of FMP and enalapril could influence the antihypertensive effects of this drug.