The effect of alterations of plasma sodium on the sodium and potassium content of bone in the rat

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.

Changes in red cell, plasma, inulin, and total water compartments in rat femurs. Comparison of vitamin D deficiency and diphosphonate induced rickets

The vascular space, as measured with the use of 99m-technetium-labelled red cells and 131I-serum albumin, as well as the 14C-inulin and 3H2O fluid compartments were measured in rats which had been made rachitic by the use of a low phosphate vitamin D-deficient diet. A similar group of rachitic animals fed vitamin D2 50 IU, 5 and 3 days prior to sacrifice and a weight-matched control group were also studied. The same spaces were measured in rats made rachitic by daily s.c. injections of ethane-1-hydroxy-1,1-diphosphonate (EHDP) for 4 weeks and a weight-matched saline injected control group. Findings indicated that the red cell and RISA spaces were unchanged in the untreated D-deficient group as compared to controls but increased after being repleted with vitamin D. By contrast, the vascular space was depressed in the EHDP-treated group. The water content was elevated in D-deficient rickets returning towards normal on healing, whilst both inulin and water spaces were increased in the EHDP-treated animals. Thus, while the extravascular space reflected the presence of osteoid, the vascular space depended on cellular turnover and the process of mineralization.