Growth factors and in particular platelet-derived growth factor (PDGF) have been implicated in the pathogenesis of glomerulonephritis and glomerulosclerosis. We have studied the distribution of immunoreactive PDGF (iPDGF) within serial kidney biopsies (days 7, 15, 30, 90 and 120) of eight rats with an accelerated form of nephrotoxic serum nephritis (NTN). The course of NTN was mild in five rats and seere in three. Two patterns of immunostain for PDGF were noted. The first consisted of iPDGF-B chain in a glomerular segmental distribution similar to that of infiltrating monocytes (OX6+cells). At all stages of NTN the distribution of iPDGF-B chain correlated closely with the immunostain for monocytes. The second pattern of immunostain showed iPDGF-A chain in a diffuse distribution along the glomerular capillary lining and to a lesser extent in some mesangial cells. In severely affected rats the magnitude of the iPDGF-A increased along with glomerulosclerosis but disappeared later from areas of segmental and global glomerular obsolescence. By contrast, in rats with milder NTN glomerular iPDGF-A chain peaked early and decreased subsequently.(ABSTRACT TRUNCATED AT 250 WORDS)