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 female Wistar rats was divided into a control group of 15 rats and an experimental group of 20 rats fed a diet supplemented with 17 mg of lead acetate per kg feed for 50 days. Total body bone densitometry (TBBMC) was performed the day before ending the 50-day experiment. On day 50, all rats were killed and their right femur and 5th lumbar vertebra were dissected. The bones were cleaned of soft tissue and femoral length and vertebral length were measured with a caliper and all bones were weighed 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 control 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 were 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-induced inhibition of axial bone development and a histomorphometric decrease in bone mass, produced mainly by enhanced resorption, and a densitometric increase in bone mass, produced by lead accumulation in bone.

Motivated by the controversy in the literature concerning the influence of activity on bone mass and on its cortical and trabecular components, a study was made using computed peripheral tomography (Stratec XCT 900) of the total, cortical, and trabecular bone mass of the dominant and nondominant upper extremities of 50 apparently normal subjects (average age 26 +/- 6 years). No differences were observed in the trabecular bone compartment, but the cortical compartment was greater (P < 0.001) in the dominant extremity. There was also a significantly greater total bone mass in the dominant extremity which we attributed to greater cortical mass (P < 0.025) given the highly significant correlation (r2 = 0.904, P = 0.0001) between total and cortical bone mass and the less significant correlation between total and trabecular bone mass (r2 = 0.479, P = 0.0001).

The hypothesis that a zinc (Zn) deficit may cause osteopenia in athletes is well founded. In rats exposed to strenous exercise, we evaluated the effect of a zinc supplement on femoral and vertebral bone mass determined by dual-energy X-ray absorptiometry. Four lots of 93-day-old female Wistar rats were studied. A control group of 30 rats were not manipulated (Zn-Ex-group). The experimental group of 40 rats was fed a diet supplemented with an additional 20% of Zn/kg of feed; this group was divided into two groups of 20 rats each, one that did not exercise (Zn؉ Ex-) and one that did (Zn؉ Ex؉). A group of 15 rats exercised but did not receive a zinc supplement (ZnEx؉ group). Training consisted of treadmill running for 5 out of 7 days over an 11-week period. Initial speed, running time, and treadmill speed were increased gradually. Analysis of variance with the Bonferroni/Dunn test showed that the length, weight, bone mineral content (BMC), and bone mineral density (BMD) of the femur were less in the Zn-Ex؉ group than in the others (p < 0.008), and the weight, BMC, and BMD of the fifth lumbar vertebra also were lower in the Zn-Ex؉ group than in the others (p < 0.008). These findings confirm the adverse effects of strenuous exercise (treadmill running) on bone tissue in rats and the effectiveness of zinc supplementation in preventing it. (J Bone Miner Res 1998;13:508-512)

No abstract

In experimental studies of bone in rats, two morphometric indices reflecting bone density have been proposed, the bone robusticity index and bone weight/ bone length index. In rats, the bone mineral content (BMC) and bone mineral density (BMD) of a selected bone can be determined using dual-energy X-ray absorptiometry (DXA); bone volume can be measured by histomorphometry and other techniques. This study was undertaken to compare two morphometric indices (bone robusticity and bone weight/bone length) with the results of DXA and histomorphometry. Forty female Wistar rats (100 days old, mean weight 239 ± 12 g) were studied: 20 controls and 20 ovariectomized rats (OVX). The morphometric indices and BMD differed significantly (Friedman test) in the overall group of rats; no differences were observed in the control group, but significant differences were apparent in the OVX group (p < 0.0001). The morphometric indices correlated more closely with BMC than with BMD; the femur length/ femur weight index had closer correlations than the robusticity index. Nonetheless, both morphometric indices differed significantly from BMD determined by DXA under abnormal conditions, which makes them unreliable for use in these circumstances.