Effects of IPP and VPP Supplementation on Blood Pressure, ACE Activity and NO Production in Spontaneously Hypertensive Rats

Abstract

This study was designed to examine the effects of supplementation of sour milk powder containing tri‐peptides, isoleucine‐proline‐proline (IPP) and valine‐proline‐proline (VPP) on blood pressure and angiotensin converting enzyme (ACE) activity and nitric oxide (NO) level in the spontaneously hypertensive rats (SHR). 6‐weeks‐old male SHR were orally administrated 1) skim milk powder (10mg/kg of BW, CON group), 2) sour milk powder with IPP and VPP (10mg/kg of BW, SMP group), 3) captopril (50mg/kg of BW, CAP group) as positive control for 8 weeks. We measured the diet consumption, body weights, and the systolic blood pressure (SBP) by tail‐cuff method weekly. The ACE activities of serum, abdominal aorta and lung were assessed. In addition, plasma nitrite level (an indicator of NO formation) was measured. As a result there were no differences in dietary consumption and body weights among the three experimental groups. After 8 weeks of treatment periods, SBP of SMP group (165.0±7.5mmHg) and CAP group (140.4±5.8 mmHg) were significantly reduced compared with those of CON group (179.1±10.4 mmHg) (p<.05). ACE activity in serum and abdominal aorta of SMP group (23.1±2.1 U/L serum and 49.4±18.5 mU/mg protein, respectively) and CAP group (23.3±2.0 U/L serum and 48.5±15.8 mU/mg protein, respectively) were significantly lower than those of CON group (26.0±2.7 U/L serum and 115.4±37.0 mU/mg protein, respectively). Plasma nitrite level was significantly higher in SMP (3.3±0.3 μM) and CAP (3.3±0.6 μM) groups than in CON (2.7±0.5 μM) group. These results imply that sour milk powder containing IPP and VPP could reduce the blood pressure through the inhibition of ACE activity and also increasing of plasma NO level in SHR.