Chemical and biological monitoring of chronic lead poisoning in the rat. Implications to the assessment of hazard of low‐level lead

Abstract

A studyon rats of the effects of lead on δ‐aminolevulinate dehydratase (ALA‐D) activity, and its pH‐dependent maximal enzyme activity is reported. Over a 5‐week period, the lead burden and ALA‐D activity in kidney, liver and brain are documented. Lead concentrations in the organs, expressed as μg/g protein are in the sequence kidney>liver> brain and reach essentially a constant level after 3 days of exposure. This is consistent with the existence of an efficient mechanism removing lead from these organs. Lead affects the ALA‐D in all three organs by reducing the activity and shifting the pH of maximum enzyme activity to more acidic values. In common with the lead levels, the ALA‐D activity does not deteriorate beyond the levels reached after 3 days of exposure. The existence of a mechanism removing lead from the organs is further supported in a recovery study on blood and kidney, in which both lead level and ALA‐D activity return essentially to normal values after 7 days of no exposure to lead.