| Zinc deficiency and lead exposure adversely affect growth and development. The molecular mechanisms of lead toxicity remain unknown. It is proposed that metallothionein (MT), a metal binding protein regulated by dietary zinc, may be a common binding protein for zinc and lead, and therefore may also regulate lead absorption and toxicity.; The objective of this study was to investigate the effects of marginal and supplemental zinc intakes on lead accumulation, toxicity, skeletal development, and MT in growing rats exposed to lead.; The marginal zinc (MZ)-fed rats had higher tissue lead and lower zinc concentrations than zinc-adequate control (C) and supplemental zinc (SZ) rats, and impaired skeletal growth, mineralization, and rates of bone formation.; In summary, the results of this study indicate that while MZ deficiency exacerbated tissue lead deposition, it generally did not intensify lead toxicity. SZ was protective against tissue lead deposition, but did not appear to directly involve MT. The detrimental effects of lead and MZ deficiency on bone development appeared to operate through different mechanisms. SZ was detrimental to BMD in the femur, suggesting that the optimal level of SZ to reduce lead absorption, while supporting growth and bone development, requires further investigation. (Abstract shortened by UMI.)... |
