Nitrite production does not always reflect nitric oxide synthesis by isolated glomeruli

The goal of this paper was the measurement of nitric oxide (NO) production in isolated rat glomeruli using two different techniques. NO production was detected directly by a NO-specific electrode and the results were compared with data measured by the Griess reaction, an indirect index to evaluate NO production. The NO production, determined by both techniques, was dependent on the number of glomeruli. Pretreatment with NW-nitro-L-arginine methyl ester, an inhibitor of the NO synthesis, reduced the NO concentration detected by the NO-sensor, but increased the NO2- concentration (when both results where compared with glomeruli without treatment). Preincubation with 1 mg/ml of Escherichia coli lipopolysaccharide significantly enhanced both NO and NO2- concentrations. Therefore, the present study provides direct evidence of NO generated in isolated glomeruli under physiological conditions and demonstrates that the measurement of NO2- by the Griess reaction, is not always an adequate technique to evaluate the actual NO production.