Endothelium-dependent vasorelaxation by Adansonia digitata L. : Possible involvement of NO and EDH in porcine coronary arteries.

INTRODUCTION: Adansonia digitata leaves are used in the traditional treatment of arterial hypertension in Senegal. The objective of this study was to determine the vasorelaxant effect of the hydro-ethanol leaf extract of Adansonia digitata (ADF) on porcine coronary arteries and to elucidate the mechanisms involved MATERIAL AND METHODS : Porcine coronary arteries were suspended in organ chambers for the recording of changes in isometric forces. Rings with intact endothelium were incubated with or without various inhibitors. L-nitro-arginin (L-NA), an inhibitor of endothelial NO synthase; Mn (III) tetrakis (1-methyl-4-pyridyl) porphyrin (MnTMPyP); Polyethylene glycol catalase (PEG-CAT); N-acetyl-L-cysteine (NAC), inhibitors of intracellular production of reactive oxygen species; Catalase (CAT), an inhibitor of extracellular reactive oxygen species; Wortmannin, an inhibitor of the redox-sensitive pathway PI3 kinase/Akt; PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine), an inhibitor of Src kinase; apamin (APA), an inhibitor of small conductance calcium-dependent potassium channels (SKCa); and Tram-34, an inhibitor of intermediate conductance calcium-dependent potassium channels (IKCa); and indomethacin (INDO), an inhibitor of cyclooxygenase, were applied before contraction with U46619 and the generation of a concentration-relaxation curve to ADF. In some experiments, the endothelium was removed before contraction with U46619 and the generation of a concentration-relaxation curve to ADF. The phosphorylation levels of Akt and eNOS were assessed by Western blot analysis. RESULTS: ADF produced 100% relaxation at 10 µg/ml in endothelium intact arteries pre-contracted with U46619. ADF induces a redox-sensitive endothelium-dependent relaxation in porcine coronary arteries. This effects is mediated by NO and endothelium-derived hyperpolarizing (EDH) whereas prostacyclins do not appear to play a role in the vascular effects. However, ADF induced sustaining phosphorylation of Akt and eNOS in endothelial cells. CONCLUSION:  Adansonia digitata induces vasodilation, which may explain its antihypertensive effect and its use in traditional African medicine.