Protopanaxatriol ginsenosides inhibit glucose uptake in primary cultured rabbit renal proximal tubular cells by arachidonic acid release

Ginsenosides are involved in protective action against renal dysfunction an d the regulation of renal functions. However, the effects of ginsenosides o n glucose reabsorption are not yet known in renal proximal tubular cells. T he aim of this study was to examine the effects of ginsenosides, protopanax adiol (PD) saponin and protopanaxatriol (PT) saponin, on alpha-methyl-D-glu copyranoside (alpha-MG) uptake and its mechanism of action in primary cultu red rabbit renal proximal tubular cells (PTCs). The alpha-MG uptake was inh ibited by 90% by 0.5 mM phloridizin and by removal of Na+ in the PTCs. Thes e are typical characteristics described for the proximal tubule. To determi ne the time- and dose-dependent effects of PD and PT saponins on alpha-MG u ptake, PTCs were incubated with different concentrations of PD and PT sapon ins (10-100 mu g/ml) and for different time periods (from 10 min to 24 h). PT saponin (greater than or equal to 50 mu g/ml) from 30 min inhibited alph a-MG uptake; however, PD saponin did not alter the alpha-MG uptake at any d oses and time periods. In the kinetic analysis of alpha-MG uptake, PT sapon in produced a significant decrease in V-max. The PT saponin induced inhibit ion of alpha-MG uptake was blocked by mepacrine, a phospholipase A(2) inhib itor. In addition, PT saponin increased [H-3] arachidonic acid release by 2 18% of that of control, and this effect was also completely blocked by mepa crine. In conclusion, PT saponin inhibited, in part, alpha-MG uptake throug h the phospholipase A(2) signal pathway in primary cultured rabbit renal PT Cs.