Endothelium-independent vasodilation induced by kolaviron, a biflavonoid complex from Garcinia kola seeds, in rat superior mesenteric arteries

Abstract

Previous studies have established the hepatoprotective, gastroprotective, hypolipidemic and hypoglycemic effects of kolaviron (KV), a biflavonoid complex from Garcinia kola seeds. In this study, we investigated the mechanisms involved in the vasorelaxant effects of KV in isolated superior mesenteric arteries from normotensive rats. KV (1, 10, 30, 100, 300, 500 and 1,000 µg/ml) concentration-dependently inhibited the contractions induced by phenylephrine (PHE) (10 µM) and KCl (80 mM) in both endothelium-intact (Emax = 58.3 ± 1.7% and 51.4 ± 1.3%, respectively) and -denuded rings (Emax = 59.3 ± 5.5% and 64.3 ± 2.4%, respectively). Furthermore, KV reduced CaCl2-induced contraction in Ca 2+ -free medium containing KCl 60 mM, thus acting as a Ca 2+ -antagonist. In addition, KV inhibited the transient contraction by PHE in Ca 2+ -free medium containing EGTA, suggesting a possible action on the release of intracellular Ca 2+ via the inositol-1,4,5-triphosphate (IP3) pathway.KV is not a specific α-adrenoceptor blocker, since it also caused a concentration-dependent inhibition of contractile responses to KCl, suggesting that KV also blocks the L-type Ca 2+ -channel. As a Ca 2+ antagonist, KV (100 µg/ml) potentiates the relaxant effects of nifedipine in denuded rings (Emax = 97.6 ± 1.2%; control = 75.1 ± 3.0%, P<0.05). Also, the vasorelaxation induced by KV was significantly inhibited after pre-treatment of the denuded rings with 4-aminopyridine (4-AP) 1 mM, a selective blocker of voltage-dependent K + (Kv) channels and,

Cardiovascular Effects Elicited by Milonine, a New 8,14‐Dihydromorphinandienone Alkaloid

“…TEA was used for blocking BK Ca channels [37], apamin for SK Ca channels [41] and charybdotoxin for IK Ca as well as BK Ca channels [42]. In our experiments, treatment with TEA (1 mM) produced a shift to the right of the concentrationresponse curve for milonine, suggesting a role for the BK Ca .…”

Cardiovascular Ion Channels as a Molecular Target of Flavonoids

“…Only recently, Matsui et al reported that apple procyanidins relax rat aortic rings possibly by activation of several potassium channels [48]. Vasodilation via synergistic effects of potassium current activation and calcium current reduction has been suggested for amentoflavone, kolaviron, pinocembrin, luteolin, and cardamonin [49][50][51][52][53]. Effects of flavonoids on vascular electrophysiology have been summarized in Table 1.…”

Sub-acute effect of NG-nitro-l-arginine methyl-ester (L-NAME) on biochemical indices ins rats: Protective effects of Kolaviron and extract of Curcuma longa L

“…[16] Also, we have shown that the vasorelaxant effects of KV in smooth muscle is mediated by mechanism that involves extracellular Ca 2+ influx blockade, inhibition of intracellular Ca 2+ release and the opening of K + channels. [17]…”