Bone mineral density at the metaphysis is specifically reduced in STZ-treated diabetic rats

Bone length (L), dry weight (DW) and ash weight (AW) were determined for the femur bone of 9-15 week old female rats with or without streptozotocin (STZ)-treatment. Matrix weight (MW) was obtained by subtracting AW from DW. AW/L3 and MW/L3 were taken as measures indicating overall bone mineral density and bone matrix density, respectively. Regional changes such as metaphyseal bone mineral density (MBD) and diaphyseal mineral density (DBD) were determined by single photon absorptiometry (SPA). In the control rats, MW/L3 and MBD stayed constant in spite of a time-dependent increase in L, whereas the other bone parameters correlated positively with L. Thus MW/L3 and MBD were compared between rats with different L, and the other parameters were compared with the expected values calculated for L by regression equation. STZ-treatment virtually stopped the growth of L, significantly reduced MBD, but hardly affected MW/L3. Although DW, AW and AW/L3 in the STZ-treated rats were significantly smaller than in the control, they were almost identical with the expected values excepting at 6 weeks when the observed values were less than the expected values. DBD in the STZ-treated rats was even larger than the expected values, DW, AW and MBD decreased with time, and MW/L3 stayed rather constant; only DBD increased time-dependently in these animals. These results suggest that bone mineralization at the metaphysis is specifically reduced in STZ-treated diabetic rats.