Investigation of terpinen-4-ol effects on vascular smooth muscle relaxation

Abstract

AimsThis study investigated the mechanisms underlying the vascular effects of terpinen-4-ol in isolated rat aortic ring preparations. Main methodsThe thoracic aortae of healthy rats were submitted to isometric tension recording. Membrane resting potential and input membrane resistance were measured by conventional microelectrode technique. Key findingsTerpinen-4-ol reversibly relaxed endothelium-containing preparations pre-contracted with high K+ and phenylephrine with IC50 values of 421.43μM and 802.50μM, respectively. These effects were significantly reduced by vascular endothelium removal. In Ca2+-free and high K+ (80mM) medium, the contractions produced by Ba2+ were reduced by terpinen-4-ol (100–1000μM) in a concentration-dependent manner. In aortic rings maintained under Ca2+-free conditions, terpinen-4-ol significantly reduced the contractions induced by either phenylephrine (1μM) or phorbol 12,13-dibutyrate (1μM). Terpinen-4-ol (10–1000μM) also relaxed the contractions evoked by BAYK-8644 (3μM) with an IC50 of 454.23μM. Neither membrane resting potential nor input resistance of smooth muscle cells was altered by terpinen-4-ol exposure. SignificanceThe present results suggest that terpinen-4-ol induced vascular smooth muscle relaxation that was preferentially due to the inhibition of electromechanical pathways related to calcium influx through voltage-operated calcium channels.