Kinetic parameters of calcium metabolism and femur morphometry in rats. I. Influence of sex and age.

The aim of this study was to establish the influence of age and sex on the kinetic and morphometric parameters of calcium metabolism. Normal values of kinetic parameters were determined in normal adult rats of different ages (4--20 months) and both sexes. Urinary hydrophyline excretion was also assessed and morphometric measurements of the femur were performed. Kinetic parameters expressed as rate constants showed a lowering of calcium turnover (kr) in the rapidly exchangeable calcium compartment until the age of 12 months and urinary and fecal rate constants (ku and kf) showed a small increase. Males exhibited a lower calcium turnover (kT) as well as lower urinary and fecal rate constants. Hydroxyproline excretion diminished with age in both sexes. Lower values were recorded in males. Morphometric parameters of femurs showed no bone loss within the examined age. The results show that differences between the sexes exist in the sense of a faster calcium turnover, higher calcium excretion rate constants, higher collagen degradation and higher bone density in adult female rats.