Abstract
It is a well known fact that the influence of age factor is very great in the susceptibility to lead poisoning. However, the reason for this phenomenon has not yet been proven. Further, there has been few studies conducted on the differences in the susceptibility, using experimental animals. The experiments were conducted to determine the relationship between the distribution of lead in the teeth and the femur of rats and their age by using 210-Pb tracer. The animals which were used in the experiments were Wistar male rats of 3 weeks, 3 months, and 22 months of age. A single intraperitoneal injection of lead nitrate solution of 210-Pb 10μCi/kg, and solutions of other densities were administered to the rats and after a lapse of 3 days, the percentages of lead intake in the femur and the teeth were measured, with results as follows.
1) Whereas the excretion of lead decreased exponentially when a small amount of lead (210-Pb 10 μCi/kg only) was administered to the control group, the excretion decreased linearly when 1 mg/kg of lead was administered. It was found that 21 days after the administration, the excretion of lead was 39.8% in the former case and 24.3% in the latter. The percetage of excretion in the feces was constantly higher than that in the urine.
2) With the increase in the dosage of lead, it was noted that the percentages of lead in the hard tissue decreased. The decrease in the percentage of lead intake was remarkable when 10 mg/kg and 100 mg/kg were administered. This tendency became predominant in the aged rats.
3) The average percentage of lead intake measured in the femur, incisor and molar of the 3 weeks old rats in the control group were 6.25%, 0.81% and 0.55%, respectively. Those of the rats of 3 months old were 2.52%, 0.76% and 0.10%, and the rats of 22 months old, 2.28, 0.97 and 0.21%, respectively.
4) In the groups of rats to which 1 mg/kg lead were administered, the average intakes of lead in the femur, incisor and molar were 2.50%, 0.37% and 0.19% respectively, in the age group of 3 weeks, 0.80%, 0.17% and 0.05% in the age group of 3 months, 0.22%, 0.07% and 0.02% in the age group of 22 months.
5) It was observed that in the suckling rats of the control group, the amount of lead was largest in the femur, but in the adult and aged rats the largest amount of lead was found in the incisor.
