Endothelium-Independent Relaxation of Alkaloid Boldine in Isolated Aortas From Normotensive and Hypertensive Rats: Participation of Ca2+ Channels

Abstract

The regulation of vascular tone plays a fundamental role in blood pressure homeostasis and still represents a significant challenge in clinical practice. Boldine, a naturally occurring alkaloid from Peumus boldus, has emerged as a compound of interest due to its therapeutic potential. This study explored boldine's vasorelaxant effects on aortas of normotensive (NTR) and spontaneously hypertensive (SHR) rats. Nω-Nitro-l-arginine methyl ester (l-NAME) (a nitric oxide synthase inhibitor), ODQ (a soluble guanylate cyclase inhibitor), and tetraethylammonium (TEA) (a nonselective K⁺ channel blocker) exerted a modest inhibitory effect, causing a rightward shift in the boldine-induced relaxation curves without significantly affecting the maximal relaxation. Boldine affected both endoplasmic reticulum-based IP3 and ryanodine receptors (RyRs) and transmembrane calcium channels in NTR aortas, whereas in SHR aortas, its actions were linked to IP3 and RyRs receptors. These findings indicate that boldine's vasorelaxant effects may contribute to vascular tone regulation through modulation of Ca2⁺ channels.