I describe a fluorometric micromethod for determining delta-aminolevulinic acid dehydratase (ALA-D) activity in whole blood. In this method, the porpho-bilinogen formed under the incubation condition using 0.05m
l of whole blood is easily converted to uroporphyrin by heating for 15 min at 100°C in an acidic medium in the presence of air. The uroporphyrin formed is a stable and highly fluorescent substance and its fluorescence intensity is measured using a spectrofluorophoto-meter.
The ALA-D activity is expressed as nanomoles of uroporphyrin formed per hour per milliliter of erythrocytes. This method offers some advantages that it is much sensitive and is employed without Ehrlich's reagent.
The erythrocyte ALA-D activity measured by the fluorometric method has a good correlation with that measured by the colorimetric method with Ehrlich's reagent (r=0.9484).
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