ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Effects of ascorbic acid (AA) on 125I-SCH 23982 binding to D1 dopaminergic receptors in membrane preparations from rat striatum were investigated. AA in the range of 0.03 µM–0.33 mM inhibited 75% of specific binding of 125I-SCH 23982 in a dose-dependent manner. At higher concentrations, this inhibition of binding activity by AA was less potent, and 3.3 mM AA inhibited only 30% of specific binding. Reduced glutathione did not alter the inhibition of binding by 0.33 mM AA, but reduced the inhibition by 3.3 mM AA to 8% of specific binding. The loss of specific binding by AA was rescued by 1 mM EDTA, an inhibitor of lipid peroxidation. In the absence of AA, competition experiments with the agonist, dopamine, revealed the presence of high-affinity (Kh = 224.9 ± 48.9 nM) and low-affinity (Kl = 21,100 ± 2,400 nM) binding sites. Although the maximum binding of 125I-SCH 23982 decreased to 40% without affecting the KD value in the presence of 1.67 mM AA, the value of the high-affinity site for dopamine was increased (Kh = 23.3 ± 9.4 nM) and that of the low-affinity site was decreased (Kl = 136,800 ± 40,900 nM). These results suggest that AA may affect D1 dopamine receptor function by lipid peroxidation, competition with dopamine for low-affinity sites, and reduced oxidation of dopamine.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.1994.63062093.x
