Methodologies for investigating the vasorelaxation action of peptides

Blood pressure is defined as the pressure of circulating blood on the wall of blood arteries. Vascular tone regulation is one of the targeted functions of small bioactive peptides, exhibiting an antihypertensive effect. Moreover, one of the vasorelaxation peptides, Trp-His, has been demonstrated to exert an antiatherosclerotic effect in mice, which suggests that vasorelaxation peptides contribute not only to appropriate blood pressure regulation but also prevent vascular diseases. Therefore evaluation of vascular function and their underlying mechanism(s) is important for understanding the physiological benefits of peptides. In this chapter, basic protocols and principles regarding experiments for evaluation of vasorelaxation action and its related vasocontractive Ca²⁺-signaling regulation of small peptides in smooth muscle cells are introduced, which will enable readers to perform these experiments successfully.