The predominance of endothelium-derived relaxing factors and beta-adrenergic receptor pathways in strong vasorelaxation induced by 4-hydroxybenzaldehyde in the rat aorta.

4-hydroxybenzaldehyde (4HB), known as ρ-hydroxybenzaldehyde, is commonly present in traditional Chinese medicine herb, most frequently used for hypertension treatment. This research aims to determine the potency of 4HB's vasorelaxant action. In the study, the vasodilation effect of 4HB was evaluated using in vitro isolated rat aortic rings assay. The aortic rings were pre-incubated with respective antagonists before being pre-contracted with phenylephrine (PE) and challenged with various concentrations of 4HB for mechanistic action studies. R (maximal vasodilation) and pEC (negative logarithm of half-maximal effective concentration) values of each experiment were determined for comparison purposes. 4HB caused vasodilation on endothelium-intact aortic rings which pre-contracted with PE (pEC = 3.53 ± 0.05, R = 100.95 ± 4.25%) or potassium chloride (pEC = 2.96 ± 0.13, R = 72.13 ± 4.93%). The vasodilation effect of 4HB was significantly decreased in the absence of an endothelium (pEC = 2.21 ± 0.25, R = 47.96 ± 4.16%). The atropine, 4-aminopyridine, Nω-nitro-L-arginine methyl ester, glibenclamide, and propranolol significantly reduced the vasorelaxation effect of 4HB. Besides that, 4HB blocked the voltage-operated calcium channel (VOCC) and regulated the intracellular Ca release from the sarcoplasmic reticulum (SR) in the aortic ring. Thus, the results indicated that 4HB exerted its vasodilatory effect via cGMP and β pathways, M-dependent PLC/IP pathways, and potassium and calcium channels.