EFFECT OF LEAD ON BONE-DEVELOPMENT AND BONE MASS - A MORPHOMETRIC, DENSITOMETRIC, AND HISTOMORPHOMETRIC STUDY IN GROWING RATS

The effect of exposure to lead on the longitudinal development of bone and on bone mass was studied in rats. A group of 35, 50-day-old femal e Wistar rats was divided into a control group of 15 rats and an exper imental group of 20 rats fed a diet supplemented with 17 mg of lead ac etate per kg feed for 50 days. Total body bone densitometry (TBBMC) wa s performed the day before ending the 50-day experiment. On day 50, al l rats were killed and their right femur and 5th lumbar vertebra were dissected. The bones were cleaned of soft tissue and femoral length an d vertebral length were measured with a caliper and all bones were wei ghed on a precision scale. Final body weight (P < 0.05), TBBMC (P < 0. 005), and femur weight (P < 0.005) were significantly lower in the con trol group. Femur length did not differ between groups, but the length of the 5th lumbar vertebra was greater in the control group (P < 0.05 ). Histomorphometry of the femur showed that Cn-BV/TV, Tb-N, Tb-Th wer e lower (P < 0.05 in all) and Tb-Sp was higher (P < 0.05) in the group given the lead-supplemented diet. These findings suggested lead-induc ed inhibition of axial bone development and a histomorphometric decrea se in bone mass, produced mainly by enhanced resorption, and a densito metric increase in bone mass, produced by lead accumulation in bone.