Establishing a rapid animal model of osteoporosis with ovariectomy plus low calcium diet in rats.

The objective of this study was to rapidly develop osteoporotic model animals by combining ovariectomy with a low calcium diet in rats. Thirty, eight-week-old, female, Sprague-Dawley rats were either sham-operated (Sham) or ovariectomized (Ovx) and divided into three groups: Sham, Ovx, and Ovx + low calcium diet. Rats in the Sham and Ovx groups were fed a standard diet containing 1.1% w/w calcium while rats in the Ovx + low calcium diet group were fed a diet containing 0.1% w/w calcium. Serum osteocalcin and bone mineral density (BMD) of the lumbar vertebrae were measured 4 and 8 weeks after surgery. The rats were euthanized 12 weeks after surgery, and the BMD of the right femur and histomorphometry of the femoral neck were assessed at that time. The Ovx + low-calcium diet group had a significantly lower mean BMD of the lumbar vertebra and higher mean serum osteocalcin concentration than the Sham and Ovx groups. Twelve weeks after surgery, rats in the Ovx + low calcium diet group had a significantly lower BMD, smaller Tb.Th and Tb.N, and larger Tb.Sp of the right femoral neck than did rats in the Sham and Ovx groups. These data indicate that a low calcium diet can significantly accelerate bone loss in ovariectomized rats. Combining ovariectomy and a low calcium diet can save considerable time in the creation of osteoporotic model animals.