Bone mineral deposition in mice selected for body conformation.

Bone mineral content was investigated in 2 lines of mice (CBi/C and CBi/L) that carry different biomasses per unit of skeletal weight. These lines also differ in their femoral histomorphometry and bone biomechanics. The logarithmic form of the allometric equation describing the relationship between ash weight and body weight was used to compare the mineral content in both sexes of these genotypes. No statistical difference was observed in the slopes of the curves describing the changes in bone mineral content as a function of age. Both lines had greater values than the line for control animals. The selected lines did differ significantly in the intercepts of the curves on the y-axis. An independent determination of both allometric parameters by genetic factors is proposed. Genes or groups of genes could affect mineral deposition in two ways: one could produce positional changes of the allometric curves in the embryo but leave their postnatal slopes unchanged; another could modify the postnatal slope of the curve. The combined expression of these different genes should be important in preserving homeostatic functioning of the organism.