Tb 611t

Isometric contractions of the coronary artery smooth muscle strips without the endothelium and adventitia were measured using a force transducer (TB-611T; Nihon Kohden, Tokyo, Japan), as previously described.¹⁷ The experimental process is briefly summarized as follows. These strips were mounted vertically in an organ bath filled with Krebs solution, gassed with 5% CO₂/95% O₂, and maintained at 37°C in a force transducer. After the relaxed smooth muscle tissue strips were stable in the solution for 15 minutes, we stimulated smooth muscle strips with 118 mM K⁺ for 5 minutes. Next, 118 mM K⁺ solution was washed out with Krebs solution. After 5 minutes, we applied resting tension. After 5 minutes of continuous resting tension, 118 mM K⁺ was used to induce depolarization contraction of smooth muscle strips for an additional 5 minutes. Next, the above cycle process was repeated until the depolarization-induced contraction caused by 118 mM K⁺ reached a maximum, that is, the resting tension was optimized. After the resting tension was optimized, the effects of posttreatment and pretreatment hesperetin on the maximum and steady-state forces of contractions induced by 30 μM SPC or 40 mM K⁺ were examined. The extent of contraction inhibition by hesperetin is described as the percentage by which the contraction induced by 30 μM SPC or 40 mM K⁺ was inhibited.