Multiple dose exposure effects on the tissue distribution of lead in the preweanling rat.

The time dependent tissue/organ distribution of Pb resulting from repeated intragastric exposure of the preweanling rat to Pb acetate was investigated. On the day of parturition, 12 dams were assigned randomly either to control (nonhandled) or Pb-treated groups and their litters were culled to 8 pups. On days 6, 9, 12, 15, and 18 post partum, the experimental groups received 50 mg Pb (as Pb acetate)/kg body weight containing 50 microCi of 210Pb. By day 7 (N = 15), the liver had accumulated 1.48 +/- 0.14 micrograms Pb/g wet weight (avg. +/- SE) and the kidney, 1.21 +/- 0.20 micrograms/g. However, most of the Pb was found in the intestine (129.07 +/- 20.90 micrograms/g) and intestinal contents (8.31 +/- 1.16 total Pb). By day 14 (N = 14), bone had accumulated 20.86 +/- 1.05 micrograms/g Pb while the liver and kidney levels had increased to 2.59 +/- 0.22 and 2.51 +/- 0.08 micrograms/g, respectively. At this time, blood was found to contain 0.87 +/- 0.07 micrograms/g and brain, 0.14 +/- 0.03 micrograms/g. On day 14, the greatest quantities of Pb were again found in the intestine and intestinal contents; 45.87 +/- 4.93 and 441.26 +/- 23.77 micrograms/g, respectively. By day 21 (N = 32), the concentration of Pb in liver, intestine, intestinal contents, and blood had decreased to 1.03 +/- 0.02, 4.22 +/- 1.68, 1.03 +/- 0.02 and 0.29 +/- 0.02 micrograms/g, respectively, while that in kidney remained unchanged (2.38 +/- 0.07 micrograms/g). By day 21, the concentration of Pb in bone and brain increased to 43.85 +/- 1.18 and 0.31 +/- 0.02 micrograms/g, respectively. However, it is to be noted that brain Pb levels were relatively low. There was no accumulation of Pb in lung, heart, stomach, or spleen at any time. Although the spleen did not accumulate any Pb, it was effected by Pb exposure as evidenced by a significant decrease in wet weight. Body weights of Pb-treated animals were comparable to those of control animals throughout the period of preweanling development.