The Effect of Lead and Aluminium on Rat Dihydropteridine Reductase
Assay of brain and liver dihydropteridine reductase (DHPR) activity was that of Craine et al. (1972). A 30% homogenate (w/v) was prepared in 0.5 M tris-maleate buffer, pH 6.8; cytosolic fraction was isolated by centrifugation at 40 000 rpm, 45 min. DHPR activity was assayed by the decrease in absorbance of nicotinamide adenine dinucleotide reduced (NADH), at 340 nm, 37 °C. Quininoid dihy-drobiopterin (qBH2) was generated with peroxidase and H2O2. The standard assay contained the following in a final volume of 1 ml: 0.05 M Tris-maleate buffer, pH 6.8; 2.5 × 10−4 M sodium azide; 10−3 MH2O2; 8 µg horseradish peroxidase; 10−4 M dimethyltetrahydropteridine (DMPH4): 10−4 M NADH and 0.2 ml DHPR source. The activity was determined as nanomoles NADH oxidised/min · mg protein.
KeywordsTyrosine Dementia Nicotin NADH Catecholamine
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