EFFECT OF REACTIVE OXYGEN SPECIES PROMOTED BY DELTA-AMINOLEVULINIC-ACID ON PORPHYRIN BIOSYNTHESIS AND GLUCOSE-UPTAKE IN RAT CEREBELLUM

1. delta-Aminolevulinic acid (ALA) has been reported to promote reacti ve oxygen species (ROS). Overproduction and accumulation of ALA, as it occurs in acute intermittent porphyria (ALP), can be the origin of an endogenous source of ROS, which can then exert their oxidative damage to cell structures. 2. To investigate the induction of lipid peroxida tion by ALA, thiobarbituric acid reactive substances and conjugated di ene formation were measured by using minimal tissue units (MTUs) obtai ned from rat cerebellum. Malondialdehyde levels increased with ALA con centration and incubation time (72% at 1.0 mM ALA and 127% at 4.0 mM A LA for 4 hr), and conjugated diene formation was enhanced 50% in incub ations with 1.0 mM ALA for 4 hr, 3. ALA-promoted ROS by exposure of ce rebellum MTUs to 1.0 mM ALA during different intervals (1-4 hr) was pa rtly reduced by the addition of antioxidants such as superoxide dismut ase (SOD; 50 U/ml), catalase (4.5 mu M) and dimethylsulfoxide (150 mM) , demonstrating the involvement of Or H2O2 and OH. in ALA autooxidatio n. 4. Porphobilinogen biosynthesis was 170% increased when cerebellum MTUs were incubated with 1.0 mM ALA for 4 hr in the presence of SOD, s uggesting that protein damage was promoted by ALA autooxidation. 5. Th ese findings provide the first experimental evidence of the involvemen t of ALA-promoted ROS in the damage of proteins related to porphyrin b iosynthesis, specially ALA-D. Oxidation of this enzyme would lead to f urther accumulation of ALA in AIP patients, which may be the origin of the well-known neuropsychiatric manifestations. (C) 1998 Elsevier Sci ence Inc.