Effects of Panax notoginseng saponins on vascular endothelial cells in vitro

AIM: To investigate the inhibition of endothelium-dependent in vitro vascul ar relaxation induced by the total saponins (gensenosides) from Panax notog inseng (PNS) and the effect of PNS on the cytosolic Ca2+ concentration on c ultured bovine pulmonary artery endothelial cells. METHODS: The endothelial -dependent vascular relaxation was assessed using acetylcholine (ACh) or cy clopiazonic acid (CPA) induced relaxation in endothelium-intact mt aorta. C ytosolic Ca2+ level was assessed in real time using dynamic digital fluores cence ratio imaging. RESULTS: In addition to its direct relaxation of the s mooth muscle cells at high concentrations, PNS, at 100 mg/L having little e ffect on smooth muscle, caused a marked inhibition of endothelium-dependent relaxation brought about by PNS. This inhibitory effect was due to its inh ibition of elevation of cytosolic Ca2+, which is required for the activatio n of NO generation and release from the vascular endothelial cells. Nifedip ine has no effect on either the endothelium-dependent relaxation or the cyt osolic Ca2+ level in the cultured endothelial cells. CONCLUSION: Our findin gs are consistent with the known action of PNS on receptor-operated Ca2+ ch annels and support our contention that PNS inhibits endothelium-dependent r elaxation by preventing the increase of Ca2+ level in endothelial cells via the receptor-operated Ca2+ channels in the presence of ACh or the non-sele ctive cation channels opened by CPA.