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

Aims This study investigated the mechanisms underlying the vascular effects of terpinen-4-ol in isolated rat aortic ring preparations. Main methods The 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 findings Terpinen-4-ol reversibly relaxed endothelium-containing preparations pre-contracted with high K + and phenylephrine with IC 50 values of 421.43 μM and 802.50 μM, respectively. These effects were significantly reduced by vascular endothelium removal. In Ca 2 + -free and high K + (80 mM) medium, the contractions produced by Ba 2 + were reduced by terpinen-4-ol (100–1000 μM) in a concentration-dependent manner. In aortic rings maintained under Ca 2 + -free conditions, terpinen-4-ol significantly reduced the contractions induced by either phenylephrine (1 μM) or phorbol 12,13-dibutyrate (1 μM). Terpinen-4-ol (10–1000 μM) also relaxed the contractions evoked by BAYK-8644 (3 μM) with an IC 50 of 454.23 μM. Neither membrane resting potential nor input resistance of smooth muscle cells was altered by terpinen-4-ol exposure. Significance The 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. [ABSTRACT FROM AUTHOR]