Effects of Panax notoginseng saponins on vascular endothelial cells in vitro.
AIM
To investigate the inhibition of endothelium-dependent in vitro vascular relaxation induced by the total saponins (gensenosides) from Panax notoginseng (PNS) and the effect of PNS on the cytosolic Ca2+ concentration on cultured bovine pulmonary artery endothelial cells.


METHODS
The endothelial-dependent vascular relaxation was assessed using acetylcholine (ACh) or cyclopiazonic acid (CPA) induced relaxation in endothelium-intact rat aorta. Cytosolic Ca2+ level was assessed in real time using dynamic digital fluorescence ratio imaging.


RESULTS
In addition to its direct relaxation of the smooth muscle cells at high concentrations, PNS, at 100 mg/L having little effect on smooth muscle, caused a marked inhibition of endothelium-dependent relaxation brought about by PNS. This inhibitory effect was due to its inhibition of elevation of cytosolic Ca2+, which is required for the activation of NO generation and release from the vascular endothelial cells. Nifedipine has no effect on either the endothelium-dependent relaxation or the cytosolic Ca2+ level in the cultured endothelial cells.


CONCLUSION
Our findings are consistent with the known action of PNS on receptor-operated Ca2+ channels and support our contention that PNS inhibits endothelium-dependent relaxation by preventing the increase of Ca2+ level in endothelial cells via the receptor-operated Ca2+ channels in the presence of ACh or the non-selective cation channels opened by CPA.