Glomeruli synthesize nitrite in experimental nephrotoxic nephritis

Abstract

Activated macrophages synthesize nitric oxide (NO) from L-arginine. In culture, the major stable end product is nitrite (NO2-). Activated macrophages accumulate in glomeruli and are responsible for injury in experimental immune complex glomerulonephritis. We examined NO2- production by isolated glomeruli and urinary NO2- in accelerated nephrotoxic nephritis in the rat. Normal glomeruli did not produce NO2- spontaneously or when stimulated with lipopolysaccharide (LPS) (1 μg/ml) or A23187 (2 μg/ml). Cultured mesangial cells at first or seventh passage did not produce NO2- spontaneously or when stimulated. Nephritic glomeruli spontaneously produced NO2- at all times studied; this production was maximal at 24 hours after induction of glomerulonephritis (158.4 ± 8.4 nmol/48 hr/ml, N = 3). The production of NO2- was inhibited 75 to 100% by NG-monomethyl-L-arginine (L-NMMA), and this inhibition was reversed by L-arginine, indicating NO2- production from L-arginine via NO. The production of NO2- was increased by LPS (1 μg/ml) at 2, 7 and 21 days. NO2- was undetectable in normal rat urine; however, it was present in urine of rats with glomerulonephritis (Day 0 to 1: 8161 ± 2605 nmol/24 hr, N = 12). The production of NO in nephritic glomeruli may have implications for both the mechanism of glomerular injury and glomerular hemodynamics.