Calcium deficiency during lactation and in the first two weeks after weaning: decreased ash and increased magnesium in bone of rat pups.

The mineral and skeletal status of offspring of calcium-deficient lactating dams was examined. At weaning pups of calcium deficient dams weigh less than controls and are hypocalcemic and hypermagnesemic, but have normal phosphorus levels. Bone ash expressed as percent dry weight is decreased, as is ash content of calcium and phosphorus, while magnesium is high. Histologically, except for thinner layers of lamellar bone, long bones and calvariae are unremarkable. Calcium-deficient pups subsequently fed a normal diet for two weeks gain weight rapidly, recover bone ash (increase of 62%) and normalize magnesium content of both blood and bone. At this point, bones from experimental and control animals are histologically indistinguishable. Weanlings of calcium-deficient mothers, themselves put onto the calcium-deficient diet for two weeks, show a further decline of blood calcium and a further decrease in bone ash. Blood and bone magnesium remain elevated. Long bone trabecular architecture and marrow cavity formation appear normal, but less compact bone is evident. These doubly deprived animals recover rapidly when placed on a normal diet. Within two weeks, mineral content of blood is in the control range, bone ash increases by 93%, and the slope of the weight gain curve parallels that of controls. However, in spite of the profound bone ash increase and linear weight gain, these animals remain deficient in both parameters when examined at 9 weeks of age. Similarly, bone mineral content, which also tended to normalize, fails to completely correct by this time point.