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Effect of exposure to low level lead on growth and growth hormone release in rats
A M Camoratto1, L M White, Y S Lau
1Department of Physiology and Pharmacology, University of Georgia, Athens 30602.
Insights
Low-level lead exposure in female pups reduced pituitary responsiveness to growth hormone releasing factor (GRF). This highlights the importance of age and sex in lead toxicity studies.
Area of Science:
- Environmental Toxicology
- Endocrinology
- Developmental Biology
Background:
- Lead exposure is a significant public health concern, particularly during development.
- Understanding the impact of low-level lead on endocrine function is crucial.
Purpose of the Study:
- To investigate the effects of prenatal and early postnatal low-level lead exposure on growth and growth hormone (GH) release in pups.
- To assess the impact of lead on pituitary responsiveness to growth hormone releasing factor (GRF).
Main Methods:
- Female pups were exposed to lead in utero.
- Body weight, food/water intake, and blood lead levels were monitored.
- Pituitary responsiveness to GRF was measured in vitro in 49-day-old pups.
Main Results:
- Prenatal lead exposure resulted in smaller female pups at postnatal day 7.
- Pituitaries from lead-exposed pups showed reduced GH release in response to GRF.
- Blood lead levels were higher in younger pups and in female pups at 49 days.
Conclusions:
- Low-level lead exposure can impair pituitary responsiveness to hypothalamic stimulation.
- Age and sex are critical factors influencing the toxic effects of lead.
- Further research is needed to understand long-term developmental impacts.
Abstract:
This study was undertaken to examine the effect of exposure to low level lead on growth and growth hormone (GH) release. Female pups exposed to lead beginning in utero were smaller than controls on postnatal day 7 (P = 0.06). There was no corresponding effect in males. No overall differences in body weights were detected in either sex with respect to treatment effect. No differences in food or water intake were observed at any time. Pituitaries from 49-day-old lead-treated pups responded to in vitro incubation with growth hormone releasing factor (GRF) with a smaller increase in GH release than those from control pups (P = 0.08). In the case of the dams, lead did not affect body weight, body length, food consumption or pituitary responsiveness; however, water consumption was significantly increased in the lactating dam (P < 0.05). Interestingly, blood lead content in 5-day-old pups (43.3 +/- 2.7 micrograms/dl) exposed to lead in utero was more than twice that of their 49-day-old litter-mates (18.9 +/- 0.7 micrograms/dl). At 49 days blood lead levels in female pups (19.94 +/- 0.8 micrograms/dl) were significantly higher than those of male pups (17.00 +/- 1.1 micrograms/dl). Maternal blood lead levels on the same day averaged 22.7 +/- 2.5 micrograms/dl. This study suggests that exposure to a low level of lead can reduce pituitary responsiveness to a hypothalamic stimulus. In addition, the data reinforce the importance of considering age and sex when evaluating the toxic effects of lead.