Koyama Masahiro, Hattori Seiji, Amano Yoshihiko, Watanabe Masanori, Nakamura Kozo
Department of Bioscience and Biotechnology, Faculty of Agriculture, Shinshu University, Minamiminowa Village, Nagano, Japan.
Department of Bioscience and Biotechnology, Graduate School of Agriculture, Shinshu University, Minamiminowa Village, Nagano, Japan.
PLoS One. 2014 Sep 15;9(9):e105802. doi: 10.1371/journal.pone.0105802. eCollection 2014.
Neo-fermented buckwheat sprouts (neo-FBS) contain angiotensin-converting enzyme (ACE) inhibitors and vasodilators with blood pressure-lowering (BPL) properties in spontaneously hypertensive rats (SHRs). In this study, we investigated antihypertensive mechanisms of six BPL peptides isolated from neo-FBS (FBPs) by a vasorelaxation assay and conventional in vitro, in vivo, and a new ex vivo ACE inhibitory assays. Some FBPs demonstrated moderate endothelium-dependent vasorelaxation in SHR thoracic aorta and all FBPs mildly inhibited ACE in vitro. Orally administered FBPs strongly inhibited ACE in SHR tissues. To investigate detailed ACE-inhibitory mechanism of FBPs in living body tissues, we performed the ex vivo assay by using endothelium-denuded thoracic aorta rings isolated from SHRs, which demonstrated that FBPs at low concentration effectively inhibited ACE in thoracic aorta tissue and suppressed angiotensin II-mediated vasoconstriction directly associated with BPL. These results indicate that the main BPL mechanism of FBP was ACE inhibition in living body tissues, suggesting that high FBP's bioavailability including absorption, tissue affinity, and tissue accumulation was responsible for the superior ACE inhibition in vivo. We propose that our ex vivo assay is an efficient and reliable method for evaluating ACE-inhibitory mechanism responsible for BPL activity in vivo.
新发酵荞麦芽（neo-FBS）含有血管紧张素转换酶（ACE）抑制剂和血管舒张剂，对自发性高血压大鼠（SHR）具有降血压（BPL）特性。在本研究中，我们通过血管舒张试验以及传统的体外、体内和一种新的离体ACE抑制试验，研究了从neo-FBS中分离出的六种BPL肽（FBP）的降压机制。一些FBP在SHR胸主动脉中表现出适度的内皮依赖性血管舒张，并且所有FBP在体外均轻度抑制ACE。口服FBP可强烈抑制SHR组织中的ACE。为了研究FBP在活体组织中的详细ACE抑制机制，我们使用从SHR分离的去内皮胸主动脉环进行了离体试验，结果表明低浓度的FBP可有效抑制胸主动脉组织中的ACE，并直接抑制与BPL相关的血管紧张素II介导的血管收缩。这些结果表明，FBP的主要BPL机制是在活体组织中抑制ACE，这表明FBP的高生物利用度，包括吸收、组织亲和力和组织蓄积，是其在体内具有优异ACE抑制作用的原因。我们认为，我们的离体试验是评估体内BPL活性相关ACE抑制机制的一种有效且可靠的方法。
