Glomeruli synthesize
nitrite (NO2-) in experimental nephrotoxic
nephritis, a model of
glomerulonephritis where infiltrating macrophages are pathogenic. NO2- synthesis was studied in active
Heymann nephritis (AHN), a model of
membranous glomerulonephritis in which macrophages have not been implicated. Active
Heymann nephritis (AHN) was induced with purified
renal tubular epithelial antigen and adjuvants. Glomeruli isolated at seven to eight weeks after induction (
proteinuria 183 +/- 28 mg/24 hr, N = 6; adjuvant controls, 1.2 +/- 0.8 mg/24 hr, N = 6) produced NO2- in culture spontaneously (7.1 +/- 1.4, adjuvant controls 2.1 +/- 0.9 nmol/2000 g/48 hours; P = 0.021) and in increased amount following LPS stimulation (12.1 +/- 2.8, controls 4.2 +/- 1.6 nmol/2000 g/48 hours; P = 0.047). Synthesis was inhibited by
L-NMMA, a competitive inhibitor of
NO synthase. Enzymic digestion of glomeruli plus staining with mouse anti-rat macrophage
monoclonal antibody ED1 showed macrophage infiltration (32 +/- 6, adjuvant controls 14 +/- 2 macrophages/glomerulus; P = 0.002). Whole body irradiation (XR) suppressed NO2- production (LPS stimulated: 1.0 +/- 0.4, N = 5; non-XR controls 7.2 +/- 4.6 nmol/2000 g/48 hours; N = 5, P = 0.016) and macrophage infiltration (1.1 +/- 0.5; non-XR controls 30 +/- 12 macrophages/glomerulus; P = 0.008) but had no effect on
proteinuria. Irradiation with renal shielding confirmed the close correlation between glomerular NO2- synthesis and glomerular macrophage numbers (rs = 0.837, P less than 0.001). These results show that macrophages infiltrate glomeruli in AHN; they are the source of NO2- in this model. Neither macrophages nor NO2- are the cause of
proteinuria.