大豆低聚肽对自发性高血压大鼠血压及血浆血管紧张素的影响

目的：探究大豆低聚肽对于大鼠血压及血浆血管紧张素的影响。方法：采用酶法制备大豆低聚肽，随后进行体外血管紧张素I转换酶（angiotensin I converting enzyme，ACE）活性抑制实验及体内实验，实验设正常对照组（正常血压大鼠（WKY大鼠）饲喂高剂量大豆低聚肽）、阴性对照组（自发性高血压大鼠（SHR大鼠））、阳性对照组（SHR大鼠饲喂卡托普利）和低、中、高剂量组（SHR大鼠饲喂0.90、1.80、4.50 g/kg大豆低聚肽），喂养30 d后，观察大鼠血压、心率、尿蛋白质量、血管紧张素II质量浓度等指标的变化。结果：大豆蛋白最佳酶解条件为：碱性蛋白酶和中性蛋白酶质量分数各0.1%、50 ℃酶解4 h，此条件下10 mg/mL大豆低聚肽ACE活性抑制率达到71.2%。经饲喂不同剂量大豆低聚肽30 d后，WKY大鼠血压变化不显著（P＞0.05），SHR大鼠血压有下降趋势；饲喂高剂量大豆低聚肽在第4周时可以显著降低SHR大鼠血压和血管紧张素II质量浓度（P＜0.05），但对于大鼠心率和尿蛋白质量无显著影响（P＞0.05）。结论：体外实验证明，与大豆蛋白相比，大豆低聚肽对于ACE活性的抑制效果更好；体内实验证明大豆低聚肽可以降低SHR大鼠的血压和血管紧张素II质量浓度，且对正常大鼠血压无明显影响，推测大豆低聚肽通过抑制ACE活性的方式发挥降压功效。

Effect of Soybean Oligopeptides on Blood Pressure and Plasma Angiotensin in Spontaneously Hypertensive Rats

Purpose: To investigate the effect of soybean oligopeptides on blood pressure and plasma angiotensin levels in rats. Methods: Soybean oligopeptides were prepared by enzymatic treatment, and its angiotensin I converting enzyme (ACE) inhibitory activity was evaluated both in vitro and in vivo experiments. Rats were divided into six groups: normal control (Wistar-Kyoto (WKY) rats with normal blood pressure rats fed high-dose soybean oligopeptides), negative control (spontaneously hypertensive (SHR) rats), positive control (SHR rats fed captopril), low, medium and high-dose groups (SHR rats fed 0.90, 1.80, 4.50 g/kg soybean oligopeptides). The feeding experiment lasted for 30 days. The changes in blood pressure, heart rate, urinary protein content and plasma angiotensin II concentration were determined during the experimental period. Results: The optimal conditions for enzymatic hydrolysis of soybean protein were found to be hydrolysis at 50 ℃ for 4 h with a mixture of alkaline protease and neutral protease at a dosage of 0.1% each. The percentage inhibition of ACE activity by soybean oligopeptides at 10 mg/mL prepared using the optimized conditions was up to 71.2%. After 30 days of feeding, there was no significant difference in blood pressure of WKY rats (P > 0.05), while the blood pressure of SHR rats had a decreasing trend in all dose groups of soybean oligopeptides. High-dose soybean oligopeptides significantly reduced blood pressure and mass concentration of angiotensin II in SHR rats at the end of the fourth week (P < 0.05), but had no significant effect on rat heart rate or urinary protein content (P > 0.05). Conclusion: Compared with soybean protein, soybean oligopeptides had better inhibitory effect on ACE activity, and could reduce blood pressure and plasma angiotensin II levels in SHR rats but without significant effect on blood pressure in normal rats. Therefore, soybean oligopeptides can exert antihypertensive effect perhaps by inhibiting ACE activity.