Other than stimulation of cell contractility, little is known on potential metabolic effects induced by sulfonylureas independently of insulin action. Previous studies from our laboratory demonstrated complete abrogation of glomerulosclerosis in an experimental model of type 1 diabetes chronically (9 month) treated with low-dose sulfonylureas. Therefore, the effects of glibenclamide (GLIB) on net collagen I, collagen IV and fibronectin medium net secretion and cell layer collagen I deposition were investigated in mesangial cells continuously exposed to 25 mM glucose for 8 weeks and treated with predetermined increasing concentrations of GLIB for the same period. Clinically relevant concentrations (0.01 µM) of GLIB fully suppressed the high glucose-enhanced accumulation of collagen I, collagen IV and fibronectin in the medium and inhibited collagen I deposition in the cell layer. These effects occurred while TGF-1 medium concentration remained elevated and glucose uptake was increased to levels above those in 25 mM glucose-incubated cultures. The decreased collagen I accumulation occurred simultaneously with enhanced collagen I mRNA expression in concert with marked suppression of PAI-1 mRNA and protein expression. This strongly suggests an accelerated matrix turnover favoring breakdown. GLIB-induced effects demonstrated a biphasic pattern, been absent or reversed in cells treated with higher GLIB concentrations (0.1 µM or 1 µM). Therefore, chronic GLIB treatment at low concentrations markedly diminishes the high glucose-induced enhanced accumulation of extracellular matrix components by suppression of steady-state PAI 1 transcriptional activity. These results and those previously reported in vivo suggest that long-term GLIB treatment may prevent glomerulosclerosis in insulin-deficient diabetes.