SEX AND STRAIN DIFFERENCES IN WHOLE SKELETAL DEVELOPMENT IN THE RAT

The dry weight and calcium content of whole skeletons was determined i n both male and female weanling, adolescent, and mature rats of the sp ontaneously hypertensive (SHR), Wistar Kyoto (WKY), and Sprague-Dawley (SD) rat strains. Dry skeletal mass, calculated as percent of body ma ss (%BM), increased with maturity in each strain. In adolescent and ma ture animals, skeletal development (%BM) was greater in female rats. S HR showed greater skeletal development (%BM) than normotensive rat str ains and this difference was detectable even in weanling animals. Desp ite these age, strain, and gender-related differences in skeletal deve lopment, the calcium content per unit skeletal mass was identical amon g the various groups examined. Regression analysis of the plot of skel etal mass as a function of body mass indicated that only a portion of mature skeletal development was related to body mass. The results show that skeletal mass developed in the rat is only partially determined by structural support demands.