Changes in the red cell, plasma and inulin spaces and in the total water contents of rat femurs in cortisone induced osteoporosis.

Measurements of the bone vascular space by use of 99mTc-labelled red cells and 131I-serum albumin, and of the 3H-inulin spaces and total water contents were carried out in female rats treated for four weeks by daily subcutaneous injections of 15 mg cortisone acetate. Significant decreases in bone vascularity, inulin space and water contents were noted as compared to controls. These changes were not associated with differences in plasma calcium values, or parathyroid gland weights. They were found to be present together with significant decreases in bone density and ash contents of the femoral shafts in the steroid-treated animals. It is suggested that the changes in the vascular and extravascular fluid spaces of bones were probably consequent upon a generally depressed level of cellular activity and bone turnover, which could be found in steroid induced osteoporosis.