OBJECTIVE To study the effect of plateletderived growth factor (PDGF) on the growth of human glomerular mesangial cells (MsC) in vitro. METHODS Immunohistochemistry for the detection of BrdU positive cells; [3H] proline incorporation for the bioactive assay of total amount of collagen; and Northern blot analysis for the determination of fibronectin (FN) alpha 1 (IV) collagen and c-myc mRNA expression. RESULTS The cell labelling index (LI) of BrdU incorporation in the PDGF group is 34.5% higher than that in the normal group, which was 19.5% (P < 0.01), The total amount of collagen secreted by MsC within cells and outside of cells in the PDGF group were 2.69 +/- 0.60% and 3.87 +/- 0.65% respectively, much higher than that of the normal group, which were 1.25 +/- 0.50% and 1.61 +/- 0.51% respectively (P < 0.01). Northern blot analysis revealed an increase of FN, Col IV, c-myc mRNA levels in the PDGF group. CONCLUSIONS PDGF can stimulate cell proliferation, synthesis of collagen and enhance FN, Col IV, c-myc mRNA expression. It is possible that PDGF may play an important role in the development and progression of glomerulopathy.