Recovery of Blood Lead Concentration and of Red Cell 8-Aminolevulinic Acid Dehydrase Activity in Dogs Following Return to Normal Diets after 75 Weeks of Lead Feeding

Blood lead concentration and red cell 8-aminolevulinic acid dehydrase (ALAD) activity were determined at intervals for eight months after symptom-free dogs, which had received 100 ppm or 500–1000 ppm of lead, by weight, in their diets for 751/2 weeks, were returned to a lead-free diet. Statistical treatment of the data disclosed a linear relationship between the the logarithm of blood lead concentration or of ALAD activity and the logarithm of time (experimental week) during the recovery period. The calculated regressions predict that recovery of ALAD will occur before recovery of the blood lead concentration. Predicted recovery times depend on the levels selected as those which must be attained for recovery to be complete, as well as on the dosage of lead. The logarithm of the slope of the ALAD recovery regression of the individual dog has a linear relation to the percentage reduction in ALAD due to the lead, the regression accounting for 92% of the variance in the recovery rates. The slope of the blood lead recovery regression has a linear relation to the increase in blood lead for the dogs which received the low lead diet, but not for those which received the high lead diet.