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Multiple dose exposure effects on the tissue distribution of lead in the preweanling rat
Insights
This study tracked lead (Pb) distribution in preweanling rats after repeated exposure. Lead primarily accumulated in the intestine early on, later shifting to bone, with minimal brain accumulation.
Area of Science:
- Toxicology
- Environmental Health
- Developmental Biology
Background:
- Lead (Pb) exposure in early development poses significant health risks.
- Understanding tissue distribution is crucial for assessing lead toxicity.
- Preweanling animals are particularly vulnerable to environmental toxicants.
Purpose of the Study:
- To investigate the time-dependent tissue and organ distribution of lead (Pb) in preweanling rats.
- To quantify lead accumulation in various organs following repeated intragastric exposure to lead acetate.
- To characterize the kinetics of lead distribution during preweanling development.
Main Methods:
- Repeated intragastric administration of lead acetate (containing 210Pb) to preweanling rats from day 6 to day 18 postpartum.
- Culling litters to 8 pups per dam and assigning dams to control or Pb-treated groups.
- Quantification of lead concentrations in liver, kidney, intestine, intestinal contents, bone, blood, and brain at different time points (days 7, 14, and 21).
Main Results:
- Lead initially accumulated predominantly in the intestine and intestinal contents.
- By day 14, significant lead accumulation was observed in bone, liver, and kidney.
- Lead concentrations in the liver, intestine, and blood decreased by day 21, while bone and brain lead levels increased; brain lead levels remained relatively low.
- No lead accumulation occurred in the lung, heart, stomach, or spleen, though spleen weight decreased significantly.
Conclusions:
- Lead distribution in preweanling rats is dynamic, with initial intestinal accumulation followed by a shift to bone.
- The study highlights the critical role of the gastrointestinal tract in early lead absorption and subsequent redistribution.
- Despite low brain concentrations, the observed tissue distribution patterns underscore the importance of monitoring lead exposure in developing organisms.
Abstract:
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.