Possible relationship between changes in [3H]DA uptake and autoxidation in rat striatal slices.

Many recent studies have suggested that oxidative damage is an important factor in several neurodegenerative disorders. Our investigations considered whether autoxidation of rat striatal slices modified dopamine uptake. Biochemical assays (TBARS, MDA-TBA complex, aldehydes, and fluorescent lipid-soluble products) and a [3H]DA uptake assay were performed on nonincubated striatal slices and on slices incubated for 150 min at 37 degreesC in Krebs-Ringer buffer without addition of free-radical generators. The results showed that spontaneous lipid peroxidation occured during incubation and that DA uptake kinetic was biphasic (high-affinity uptake1 and low-affinity uptake2) with a significant decrease of maximal velocity of uptake. Ascorbate, a known antioxidant, was used to determine whether a relationship existed between lipid peroxidation and reduced dopamine uptake. Addition of ascorbate (100 and 500 microM) in Krebs-Ringer buffer for 150 min at 37 degreesC failed to indicate whether decreased [3H]DA uptake resulted from lipid peroxidation. In fact, ascorbate acted as a prooxidant, only preventing decreased DA uptake2 at 100 microM. Trolox, another antioxidant, inhibited lipid peroxidation by about 95% with a concentration of 700 microM and protected only uptake1. With a concentration of 5000 microM, Trolox also protected uptake2. On the whole, these results indicate that spontaneous autoxidation in rat striatal slices was associated with a lipid peroxidation process that altered the DA uptake system.