Monocytes and macrophages in focal glomerulosclerosis in Zucker rats.

It has been recently suggested that focal glomerulosclerosis (FGS) is analogous to atherosclerosis. Obese Zucker (OZ) rats spontaneously develop hyperlipidemia, proteinuria and FGS. To evaluate the role of the monocyte (MO) and its derivatives in the pathogenesis of the lesion, 30 OZ rats and 15 lean littermates (LZ) were followed for up to 240 days of age. At 75, 120 and 240 days of age, groups of 10 OZ and 5 LZ were assessed with respect to serum total and free cholesterol (TC and FC), triglyceride, lipoprotein electrophoresis, renal histology, histochemistry and immunohistochemistry. All serum lipids were raised at 75 days in OZ rats and increased progressively at 120 and 240 days. The early lesions of FGS were first demonstrated in OZ at 120 days with more advanced lesions at 240 days. FGS was seen in LZ only at 240 days when their serum lipids were raised. Intraglomerular MO infiltration was significantly higher in OZ than in LZ at all time periods (p less than 0.01) and greater in glomeruli with FGS lesions than in those without (p less than 0.01 and 120 days and p less than 0.05 at 240 days). Staining for ED1 and Ia antigens with monoclonal antibodies demonstrated increasing numbers of intraglomerular ED1+ and Ia+ cells with increasing age and extent of FGS. The findings suggest a role for intraglomerular macrophages in the pathogenesis of FGS in OZ.