Hinokitiol produces vasodilation in aortae from normal and angiotensin II- induced hypertensive rats via endothelial-dependent and independent pathways.

Hinokitiol is a natural bioactive compound with numerous pharmacological properties. Here, we aimed to examine hinokitiol's effects on vascular relaxation. Cumulative relaxation responses to hinokitiol were assessed in isolated aortae from normotensive and angiotensin II-induced hypertensive rats in the presence and absence of selective inhibitors. Hinokitiol produced vasodilation of phenylephrine preconstricted aortae using both normotensive and hypertensive rats. In normotensive rats, hinokitiol's vasodilation was reduced by endothelial denudation and nitric oxide synthase (NOS), guanylate cyclase, and cyclooxygenase inhibition. Also, hinokitiol vasodilation was attenuated by β-receptors, adenylate cyclase, Ca-activated K channels and hyperpolarization inhibition. Moreover, hinokitiol exhibited a blocking activity on Ca mobilization through voltage dependent Ca channels (VDCC). However, its effect was not changed by muscarinic receptor and Sarc-K ATP channels blocking but was enhanced by blocking voltage-dependent K channels. However, in angiotensin II-induced hypertension, hinokitiol vasodilating activity was attenuated by NOS inhibition and it blocked Ca mobilization through VDCC, while its vasodilation was partially attenuated by Sarc-K ATP channels blocking. However, the vasodilating effect of hinokitiol was not attenuated by either cyclooxygenase, β-receptor, Ca-activated K channels, or voltage-dependent potassium channels inhibition, but was enhanced by blocking hyperpolarization. Hinokitiol's vasodilating effect in normotensive and hypertensive vessels is mediated through both endothelium-dependent and endothelium-independent mechanisms.