[Distribution of bone tissue renewal processes in the skeleton of rats on a hypocaloric diet]

The present study was undertaken to confirm if the mechanical forces can control the pattern of bone turnover as previously demonstrated in our researches on the skeleton of dog. The bone turnover pattern in spongy and compact long bones of lactating female rats submitted to a Calcium deficient diet has been investigated. One group of female rats was maintained on a Ca++ deficient diet for 10 days and a second group for 30 days. Both groups were submitted after this period to a normal diet for 10 days. A third group of female rats of the same age maintained to a normal diet was used as control. The results obtained are in agreement with our previous researches and indicate that mechanical stresses appreciably control the bone turnover pattern. In fact the diminished assumption of Ca++ with diet has caused bone loss at first in the metaphyseal deeply located spongiosa, region less essential to mechanical resistance; only if the ipocalcic diet is protracted, the epiphyseal spongiosa and compact bone of the metaphysis and diaphysis -more heavily mechanical loaded portions of the long bones- were removed.