This study describes a potential of Phytolaccaceae (Phytolacca americana var.) as an inhibitor of high glucose-stimulated production of extracellular matrix (ECM) proteins and TGF-beta in cultured glomerular mesangial cells (GMCs). Raising the ambient glucose concentration for 24 hrs caused a dose-dependent increase in [3H]thymidine incorporation of GMCs, and the maximal response was achieved at 20 mM. Phytolaccaceae extracts (2.5-20 microg/ml) inhibited the high glucose-induced [3H]thymidine incorporation in a dose-dependent manner, and the concentrations tested here did not affect to the cell viability. Exposure of the GMCs to 20 mM glucose caused both ECM (collagen and fibronectin) accumulation and TGF-beta secretion, and these changes were significantly diminished by treatment of GMCs with Phytolaccaceae (10 microg/ml). Taken together, these results indicate that Phytolaccaceae inhibits the high glucose-induced GMCs proliferation partially through suppressing accumulation of ECM components and TGF-beta production, suggesting that Phytolaccaceae may be a promising agent for treating the development and progression of diabetic glomerulopathy.