METHOD FOR PRESERVING ERYTHROCYTIC DELTA-AMINOLEVULINIC-ACID DEHYDRATASE ACTIVITY THAT FACILITATES POPULATION STUDIES ON LEAD-INTOXICATION

A method preserving the activity of the erythrocytic enzyme delta-amin olevulinic acid dehydratase (EC 4.2.1.24) was developed using a vehicl e of 50% aqueous glycerol containing dithiothreitol (80 mu M). Whole h eparinized blood (0.5 ml) was added to 0.75 ml of this mixture in a cr yovial tube (capacity 1.3 ml), mixed well and stored in a freezer at - 20 degrees C for 21 days. Statistical comparison of the enzyme activit y when freshly assayed and after storage indicated excellent agreement for quantitation of the non-activated enzyme (intraclass correlation coefficient = 0.99) and the activated enzyme (intraclass correlation c oefficient = 0.98). This storage method will facilitate future populat ion studies on lead intoxication, particularly those in remote locatio ns.