Fig. 4.

Role of Fenton chemistry in the production of NOx from L-NAME. A-B) NOx production from incubation of L-NAME in A) NaAscH or H₂O₂ in the presence and absence of Fe²⁺, SOD1, and catalase, in HEPES buffer for 3 h or in B) plasma or peritoneal fluid (centrifuged at 3000 rpm for 10 min to remove cells) in the presence and absence of catalase for 24 h. Chemicals, as given in each column of the table, were mixed and incubated. Proposed Fenton-related reaction equations are shown as inserts in (A). C) NOx production from incubation of L-NAME in different biomatrices. Fresh tissues from adult sheep were homogenized in HEPES buffer (1 g tissue in 8 ml). The supernatant obtained after centrifugation at 3000 rpm for 10 min was incubated with 25 mmol/L L-NAME for 24 h. For each biomatrix, a time-control sample without L-NAME was subtracted to calculate NOx production from L-NAME. D) NOx production from incubation of L-NAME in different biomatrices that could be eliminated by catalase. (D) is the difference between (C) and a parallel experiment that was performed in the same manner as (C) except for the addition of 1 mg/mL catalase before incubation. One-way ANOVA for (C-D). All incubations were in HEPES at 37 ^oC in the dark while exposed to room air, and measured by triiodide-based chemiluminescence. n ≥ 3.