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Kinetic observations in neonatal mice exposed to lead via milk
I Palminger Hallén1, S Jönsson, M O Karlsson
1Toxicology Division, National Food Administration Uppsala, Sweden.
Insights
Lead absorption in infant mice is rate-limited, with delayed peak blood lead levels occurring 50-74 hours post-exposure. This suggests milk
Area of Science:
- Toxicology
- Developmental Biology
- Environmental Health
Background:
- Lead exposure in infants is a significant public health concern.
- Understanding lead absorption and disposition in developing organisms is crucial for risk assessment.
- Conflicting data exists regarding milk's influence on lead absorption in infant rodents.
Purpose of the Study:
- To investigate the pharmacokinetics of lead absorption and disposition in suckling mice.
- To elucidate the mechanisms underlying lead absorption via milk in neonates.
- To clarify the role of milk in lead bioavailability in immature rodents.
Main Methods:
- Lactating dams were administered intravenous 203Pb.
- Lead concentrations in suckling offspring blood were monitored for 10 days.
- Kinetic analysis was performed on pups' blood lead data.
Main Results:
- Maximum blood lead concentrations in pups peaked between 50-74 hours post-administration.
- Lead absorption in pups was rate-limited, with an absorption half-life of approximately 17 hours.
- Lead distribution to peripheral tissues differed between suckling mice and adults.
Conclusions:
- Delayed lead absorption in pups is likely due to casein-bound lead retention in the ileal mucosa.
- The milk diet may contribute to the increased lead absorption observed in immature rodents.
- Temporal variations in lead absorption measurements may explain conflicting findings in previous studies.
Abstract:
The absorption and disposition of lead in blood was examined in 10-day-old suckling mice exposed via milk. Lactating dams were administered a single intravenous injection of 0.05 mg Pb (2.5 mCi 203Pb)/kg body wt. Lead concentrations in blood of the suckling offspring were measured for 10 days after administration to the dams. Maximum blood lead concentrations in the pups were recorded between 50 and 74 hr after dams' administration despite the fact that the majority of the lead dose to the sucklings was delivered within 24 hr after dams' administration. Kinetic analysis of pups' blood lead data revealed a rate-limited absorption in the suckling pups with an absorption half-life of approximately 17 hr in the pups. This delayed absorption is most likely due to a retention of casein-bound lead in the ileal mucosa which has a high pinocytotic activity of dietary proteins in infant rodents. The present results also indicated that the distribution of lead to the peripheral tissues in the suckling mice was different than that of adults. The conflicting evidence on whether milk enhances or inhibits the absorption of lead in infant rodents may thus be explained by measurements of lead absorption at different time periods after administration to the animals. It is also suggested that the milk diet is one reason for the increased absorption of lead seen in immature rodents.