Vasorelaxation effect of 18β-glycyrrhetinic acid on the thoracic aorta of rats. - GreenMedInfo Summary

18β-Glycyrrhetinic acid (18β-GA) is an effective component extracted from the traditional Chinese medicine(Leguminosae) and has various biological activities. This study was performed to investigate the vasodilatory effects of 18β-GA on isolated rat thoracic aortic rings and explore the underlying mechanisms. The rings were obtained from normal Sprague-Dawley rats and then precontracted with norepinephrine (NE) (1 μM) or KCl (60 mM). 18β-GA (1.883-11.297mg/L) was added successively by cumulative dosing to observe and record the changes in the tension of the vascular ring. The effects of NG-nitro-l-arginine methylester (L-NAME), indomethacin (INDO), barium chloride (BaCl₂), 4-aminopyridine(4-AP), tetraethylammonium (TEA), and glibenclamide on the vascular diastolic function of 18β-GA were determined. 18β-GA substantially exhibited a dose-dependent vasorelaxant effect on the NE-induced and KCl-induced contractions of the rings. The integrity of the vascular endothelium had no influence on the 18β-GA-induced vasorelaxation effect in the rings. L-NAME and IDON showed no significant differences in their effects on this vasorelaxation process in the rings precontracted with NE. This result suggests that the vasorelaxation mechanism of 18β-GA may be independent of the vascular endotheliumBaCl₂ and 4-AP antagonized the vasorelaxation effect of 18β-GA, but TEA and glibenclamide showed no remarkable effect on the vasodilation of 18β-GA. Findings suggest that 18β-GA induces vasorelaxation in thoracic aortic rings via the receptor-operated Cachannels and voltage-operated Cachannels and the opening of inward rectifier potassium channels and voltage-operated potassium.