Potassium Channels Contributes to Apelin-induced Vasodilation in Rat Thoracic Aorta

Apelin is a newly discovered peptide hormone and originally discovered endogenous apelin receptor ligand.

In this study, we aimed to investigate the possible roles of potassium channel subtypes in the vasorelaxant effect mechanisms of apelin.

The vascular rings obtained from the thoracic aortas of the male Wistar Albino rats were placed into the isolated tissue bath system. The resting tension was set to 2 g. After the equilibration period, the aortic rings were precontracted with 10-5 M phenylephrine (PHE) or 45 mM KCl. Pyroglutamyl-apelin-13 ([Pyr1]apelin-13), which is the dominant apelin isoform in the human cardiovascular tissues and human plasma, was applied cumulatively (10^-10-10-⁶ M) to the aortic rings in the plateau phase. The experimental protocol was repeated in the presence of specific K⁺ channel subtype blockers to determine the role of K⁺ channels in the vasorelaxant effect mechanisms of apelin.

[Pyr1]apelin-13 induced a concentration-dependent vasorelaxation (p < 0.001). The maximum relaxation level was approximately 52%, according to PHE-induced contraction. Tetraethylammonium, iberiotoxin, 4-Aminopyridine, glyburide, anandamide, and BaCl2 statistically significantly decreased the vasorelaxant effect level of [Pyr1]apelin-13 (p < 0.001). However, apamin didn't statistically significantly change the vasorelaxant effect level of [Pyr1]apelin-13.

In conclusion, our findings suggest that BK_Ca, IK_Ca, Kv, K_ATP, Kir, and K_2P channels are involved in the vasorelaxant effect mechanisms of apelin in the rat thoracic aorta.