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Duodenal uptake of lead by suckling and weanling rats
Insights
Lead (Pb) absorption in young rats primarily occurs in the duodenum, not the ileum. This absorption is enhanced in fasted pups, indicating milk diet influences lead uptake.
Area of Science:
- Toxicology
- Developmental Biology
- Gastroenterology
Background:
- Lead (Pb) exposure is a significant public health concern, particularly for infants and children.
- Understanding the developmental changes in lead absorption is crucial for risk assessment.
Purpose of the Study:
- To determine the primary site of lead absorption in suckling rats.
- To investigate the age-dependency of lead absorption and retention.
- To assess the influence of the milk diet on lead absorption.
Main Methods:
- Intragastric administration of 203PbCl2 and Pb-acetate to rat pups of different ages.
- Measurement of mucosal uptake of Pb in various regions of the small intestine at different time points.
- Comparison of Pb uptake in suckled versus fasted pups.
Main Results:
- Duodenal mucosal uptake of Pb was significantly higher in 10- and 14-day-old pups compared to other intestinal regions.
- Duodenal Pb uptake diminished by 24 days of age.
- Ileal uptake represented retention and was also age-dependent.
- Fasted pups exhibited substantially higher duodenal Pb uptake and blood Pb levels than suckled pups.
Conclusions:
- Lead absorption in suckling rats occurs predominantly in the duodenum.
- Ileal uptake reflects intestinal retention rather than absorption.
- The milk diet plays a role in modulating Pb absorption, with fasting enhancing duodenal uptake.
Abstract:
The aim of the current study was to determine the site of absorption of Pb by suckling rats. When 203PbCl2 (carrier-free) plus Pb-acetate (50 micrograms/g BW) was intragastrically administered to rat pups aged 10 and 14 days, mucosal uptake of Pb, measured 2 h after intubation, was manyfold greater in the duodenum than in other regions of the small intestine. By 24 days of age, this duodenal uptake was no longer apparent. In suckling pups the duodenal content of Pb became undetectable by 24 h postintubation; in contrast, ileal uptake was minimal at 2 h but increased progressively through 24 h. The ileal uptake component was also age-dependent, having disappeared by 24 days of age. These findings suggest that it is the duodenum where Pb absorption occurs, whereas ileal uptake represents intestinal retention. To assess the role of the milk diet in the elevated Pb absorption by the duodenum of suckling animals, the effect of fasting following intubation was determined. The duodenal uptake of Pb was substantially higher in fasted pups than in suckled littermates. Correspondingly, blood Pb levels were more than 4-fold higher in fasted pups than in suckled pups. We conclude that the enhanced absorption of Pb in the suckling rat is due to duodenal absorption and that this absorptive process is even further enhanced in the absence of milk.