Effects of Lead Exposure on Skeletal Development in Rats

The effects of lead on growth in female rats and on growth andskeletal development in their offspring were investigated. Noalteration in growth rate, compared to the growth rate in pair-fedcontrols, was observed in 48 weanling females continuously exposedto 250 or 1000 ppm lead in drinking water and fed a repletediet. After 49 days of exposure, all rats (24 pair-fed controls,12 exposed to 250 ppm lead, and 12 exposed to 1000 ppm lead)were mated with control males. At parturition, six lactatingdams each from the 250 and 1000 ppm lead groups were removedfrom lead exposure and given control drinking water, and sixlactating dams each from the control group were given either250 or 1000 ppm lead in drinking water. Exposure conditionsfor the remaining dams in the control, 250, and 1000 ppm groupswere not changed. Maternal blood lead in the continuously lead-exposedgroups was higher at the end of lactation than prior to mating.Lead exposure prior to parturition caused greater maternal tibiallead accumulation than lead exposure after parturition. In contrast,lead exposure prior to parturition had a lesser impact on offspringtibial lead accumulation than lead exposure after parturition.Decreases in tibial calcium and phosphorus were observed indams exposed continuously to 250 or 1000 ppm lead; however,there was no apparent effect of lead on maternal growth-platemorphology or on growth-plate width. Offspring body weight wasdepressed relative to controls during suckling (Day 11) andafter weaning (Day 24) in high-dose and continuously lead-exposedgroups. Continuous lead exposure caused a greater decrease inoffspring body weight than lead exposure only prior to or afterparturition. Decreased tail length growth suggested possibleeffects of lead on tail vertebral bone growth. While tibialcalcium and phosphorus levels were not changed in the weanlings,increased weanling growth-plate width, with disruption of chondrocyteorganization, and wider metaphyseal trabeculae were observed.Although the mechanisms of these effects are not known, theresults suggest that local lead-related effects on growth-platechondrogenesis and metaphyseal mineralization may be involved.