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

Abstract

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 IC50 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 IC50 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.

Keywords: Excitation–contraction coupling; Monoterpenoids; Terpinen-4-ol; Vascular smooth muscle; Vasorelaxant.