Calcium channel blocking activity of calycosin, a major active component of Astragali Radix, on rat aorta1

Abstract

Aim: To investigate the vasoactivity of calycosin, a major active component of Astragali Radix. Methods: Experiments were performed on isolated rat thoracic aortic rings pre-contracted with phenylephrine (PHE) or KCl. Results: Calycosin produced a concentration-dependent relaxation on the tissue pre-contracted using PHE with 4.46±0.13 of pD 2 and 95.85%±2.67% of E max ; or using KCl with 4.27±0.05 of pD 2 and 99.06%±2.15% of E max , and displaced downwards the concentration-response curves of aortic rings to PHE or KCl. The relaxant effect of calycosin on denuded endothelium aortic rings was the same as on intact endothelium aortic rings, and its vasorelaxant effect was not influenced by L-NAME or indomethacin. In Ca 2+ -free solution, calycosin (30 µmol/L) did not have an effect on PHE (1×10 -6 mol/L)-induced aortic ring contraction. The effects of calycosin and nifedipine where somewhat different; calycosin decreased aortic ring contractions induced by the two agonists, but nifedipine displayed a more potent inhibitory effect on KCl-induced contractions than on PHE-induced contractions, and the vascular relaxing effects of calycosin and nifidipine were additive on PHEinduced contraction but not KCl-induced. Conclusion: Calycosin is a vasorelaxant. Its action is endothelium-independent and is unrelated to intracellular Ca 2+ release. It is a noncompetitive Ca 2+ channel blocker. The effect of calycosin on Ca 2+ channel blockade may be different from that of dihydropyridines. This study demonstrated a novel pharmacological activity of calycosin, and supplied a theoretic foundation for Astragali Radix application.

Calycosin and Formononetin Induce Endothelium‐Dependent Vasodilation by the Activation of Large‐Conductance Ca2+‐Activated K+ Channels (BKCa)

“…Besides, we also observed some discrepancies in the effects of calycosin and formononetin in blood vessels from various vascular beds. Previous study intact aortic rings reported that the relaxation elicited by calycosin was endothelium-independent by acting as Ca 2+ channel blocker [7]. However, here in rat mesenteric arteries we observed that calycosin-elicited relaxation is both endothelium-dependent and endothelium-independent.…”

“…Previous studies have shown that calycosin and formononetin produced antihypertensive effects and improved endothelial and cardiovascular functions [3–6]. They have been shown to display vasoactive effects in various vascular beds [3, 5–7]. In rat aorta, calycosin induced vasodilation mainly by inhibiting voltage-dependent Ca 2+ channel (VDCC) in vascular smooth muscle [7], while formononetin caused vasodilation by releasing nitric oxide (NO) in endothelial cells, as well as by the activation of large-conductance Ca 2+ -activated K + (BK Ca ) and ATP-sensitive potassium (K ATP ) channels in aortic smooth muscle cells [6].…”

“…They have been shown to display vasoactive effects in various vascular beds [3, 5–7]. In rat aorta, calycosin induced vasodilation mainly by inhibiting voltage-dependent Ca 2+ channel (VDCC) in vascular smooth muscle [7], while formononetin caused vasodilation by releasing nitric oxide (NO) in endothelial cells, as well as by the activation of large-conductance Ca 2+ -activated K + (BK Ca ) and ATP-sensitive potassium (K ATP ) channels in aortic smooth muscle cells [6]. In addition, these two isoflavonoids were reported to ameliorate cerebral ischemia and reperfusion injury by improving endothelial dysfunction [8, 9].…”

Cardiovascular Ion Channels as a Molecular Target of Flavonoids

“…The authors suggested that inhibition of calcium influx might be involved in the observed vasorelaxant effect. Inhibition of vascular calcium current has also been reported for the natural flavonoid calycosin isolated from Astragali radix, the flavonoid containing extract of Sarcococa saligna, and the plant-flavonoid catechin [17][18][19]. Effects of the main green tea flavonoid epigallocatechin (EGCG) on vascular preparations have been studied in detail.…”

Slimpid May Boost Plasma IGF-1 Level and Improve the Quality of Life in Patients with Risk of Developing Metabolic Syndrome

“…In the present study, the CM approach was adopted for the assessment of the efficacy of a Chinese herbal formula, Slimpid, in patients possibly with MS or at risk of developing MS. Though the actual mechanism of the treatment efficacy is not yet known, most of the ingredients of Slimpid are traditionally believed to exert anti-ageing effects [23], possibly by regulating both Yin and Yang, via regulating endocrine and metabolic functions. Such effects refer to as "supplementing Qi to strengthen Pi" and "eliminating inner-heat and dampness" in the context of Chinese medicine.…”