Maternal and weanling bone: The influence of lowered calcium intake and maternal dietary history

Abstract

Skeletal changes in the dam during lactation (a period of skeletal depletion) and the post-lactation period (a time of skeletal repletion) are of interest as a model for the study of mineral metabolism. With the introduction of lowered calcium (Ca) intake during gestation, lactation and the postpartum period, the model can be used to investigate factors that contribute to the development and maintenance of peak bone mass. We have employed this model in the rat with varied calcium intake during gestation, lactation and neonatal growth. In one experiment, dams were maintained on 0.02% Ca during gestation-lactation; at the end of lactation vertebral bone showed decreased bone area, increased osteoid surface and increased osteoblast numbers compared with controls. Trabeculae showed woven bone and diffuse tetracycline label. Offspring from these dams maintained on 0.02% Ca post-weaning weighed less and incurred spontaneous fractures and mortality. In the second experiment dams maintained on 0.5% Ca showed a bone mineral depletion (by single photon densitometry) on days 6 and 19 of lactation, which did not resolve until 28 days post-weaning. Control dams on 1.0% Ca showed no statistically significant depletion nor post-weaning repletion. The third study examined bone mineral content of pups born to 0.5% or 1% Ca-intake dams. Offspring from 0.5% dams retained a bone mineral content deficit despite being fed 1% Ca post-weaning. Offspring from 1% dams placed on 0.5% Ca post-weaning also showed a mineral deficit. Offspring data point to the influence of maternal Ca intake during gestation/lactation. Maternal data point to the import of adequate dietary Ca to maintain the dam's bone quality and quantity during the reproductive and post-reproductive periods.