Delta-aminolevulinic acid dehydratase (EC4.3.1.24) activity in erythrocytes from cattle administered low concentrations of lead acetate

Abstract

Four different age groups of cattle, which had never been exposed to Pb, were used to determine normal age-related values for erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity. Acute or chronic Pb intoxication was experimentally induced in young calves, and their ALAD values were compared with the normal values. Results indicated that ALAD of normal bovine erythrocytes increased 2- to 3-fold from 1 week to 9 weeks of age and then slowly returned to the initial (1 week old) value by 9 months of age. Erythrocyte ALAD from cattle greater than or equal to 9 months old was uniform. Because of the age-related changes in normal ALAD of cattle less than 9 months old, the age of an animal should be carefully established and age-matched controls evaluated simultaneously when ALAD is used to assess calves suspected of having Pb poisoning. A significant negative correlation was found between blood Pb concentration and ALAD during the first 24 hours after the initial administration of Pb, indicating a high sensitivity of erythrocyte ALAD to Pb. However, when blood Pb concentrations reached 50 micrograms/dl, ALAD did not change further. Because single ingestions of Pb can raise blood Pb concentrations greater than 50 micrograms/dl, ALAD appears to have little value in differentiating acute from chronic Pb intoxication. Within 7 days after Pb administration ceased, ALAD did not increase significantly, even when calves were given calcium ethylenediaminetetraacetic acid (CaNa2EDTA); however, blood Pb concentration decreased by 50%. The rapid change in blood Pb concentration gave a false indication of a positive treatment effect when no real effect was detected by ALAD.(ABSTRACT TRUNCATED AT 250 WORDS)