The Contractive Effect of <i>Rubia tinctorum</i> L. Extract on the Isolated Aorta Smooth Muscle and Its Protective Effect Against the Damage Caused by Hyperglycemic Solution in Rat

Abstract

Background: Few past studies have indicated antispasmodic and anti-oxidative effects of some species of Rubiaceae. Objectives: This study aimed to investigate the effect of hydroalcoholic extract of Rubia tinctorum L. (madder) root on the rat-isolated aorta and possible protective effects against the damage caused by hyperglycemic environment. Methods: The isolated thoracic aorta ring (with or without endothelium) was treated with phenylephrine (10-6 M) or KCl (80 mM) plus madder (0.1, 0.5, 1, and 5 mg/mL) and madder alone. The effect of madder alone and combined with phenylephrine (10-6 M) was studied in Ca2+-free Krebs. To investigate the effect of madder on aorta under oxidative stress, the aorta response to acetylcholine (10-5 M) following three hours incubation with high glucose (44 mM) with or without madder (0.5 mg/mL) was measured. Results: Madder did not have any significant effect on pre-contracted aorta with phenylephrine or KCl; however, madder alone could contract aorta concentration dependently (P < 0.01). In Ca2+-free Krebs, the contractile responses of aorta to madder or madder plus phenylephrine reduced up to 60% (P < 0.05). After three hours incubation of aorta ring with high glucose, aorta response to acetylcholine was vasoconstriction. Adding 0.5 mg/mL madder to hyperglycemic solution apparently preserved acetylcholine vasodilatory effect on aorta (P < 0.01). Conclusions: Our findings suggest that madder induces a vasoconstriction effect on aorta in vitro, which probably is related to facilitated entry and sensitivity of muscle cells to calcium. Madder also may have protective effects in aorta, probably against oxidative damage of high concentration glucose.