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Bioavailability of lead from various milk diets studied in a suckling rat model
1Toxicology Division, Swedish National Food Administration, Uppsala, Sweden.
Insights
Lead bioavailability in suckling rats varied significantly by diet. Human milk and infant formula showed higher lead absorption than cow
Area of Science:
- Toxicology
- Nutritional Science
- Pediatric Health
Background:
- Lead exposure is a significant public health concern, particularly for infants.
- Understanding lead bioavailability from different milk sources is crucial for assessing infant risk.
- Dietary components can influence the absorption and toxicity of heavy metals.
Purpose of the Study:
- To investigate the bioavailability of lead from various milk diets in suckling rats.
- To compare lead absorption and distribution following administration of human milk, infant formula, cow's milk, and rat milk.
- To correlate blood and brain lead levels with dietary intake.
Main Methods:
- Suckling rats (14-day-old) were gavaged with 203Pb-labeled diets (human milk, infant formula, cow's milk, rat milk, deionized water).
- Radioactivity was measured in tissues at 2 and 6 hours post-administration.
- Lead distribution within milk fractions (cream, whey, casein) was analyzed in vitro.
Main Results:
- Lead bioavailability at 2 hours: water (47%) > human milk (42%) > infant formula (40%) > cow's milk (31%) > rat milk (11%).
- After 6 hours, bioavailability remained high for water and human milk, moderate for formula and cow's milk, and lowest for rat milk.
- Blood and brain lead levels were higher in pups fed human milk compared to rat milk, correlating with total body uptake.
- Intestinal lead absorption sites varied, with higher uptake in the duodenum for water/human milk and ileum for rat/cow's milk.
Conclusions:
- The milk diet significantly influences lead bioavailability and tissue distribution in suckling rats.
- Human milk and infant formula facilitate greater lead absorption compared to cow's milk and rat milk.
- These findings highlight the importance of dietary composition in mitigating lead toxicity in infants.
Abstract:
The bioavailability of lead from various milk diets was studied in 14 day old suckling rats. Human milk, infant formula, cow's milk, rat milk and deionized water labeled with 203Pb were given to rat pups by gastric intubation. Animals were killed after 2 or 6 h and the radioactivity in the tissues was measured. At 2 h after administration the lead bioavailability, defined as lead uptake in the body, excluding the gastrointestinal tract, was 47% from water, 42% from human milk, 40% from infant formula, 31% from cow's milk and 11% from rat milk. After 6 h the bioavailability of lead was about 50% from water and human milk, 45% from infant formula and cow's milk, and 36% from rat milk. The blood lead levels in the pups reflected the total body uptake and were also correlated to the brain lead levels. Thus, rat pups given lead in human milk had approximately twice as high lead levels in blood and brain than pups given lead in rat milk. The intestinal absorption of lead was dependent on the milk diet given to the sucklings. In duodenum, the highest uptake of lead was found in rats given water or human milk, whereas in rats given rat or cow's milk the highest uptake of lead was found in ileum. The distribution of lead in cream, whey and casein fractions of the milk diets after in vitro labeling with 203Pb was also studied. The casein fraction in cow's and rat milk contained 90-96% of the total amount of lead in the diet.(ABSTRACT TRUNCATED AT 250 WORDS)