The Effect of Elcatonin on Bone Metabolism in Ovariectomized Rats

Abstract

Although elcatonin increases the bone mineral density, the optimal effective dose of elcatonin in clinical or experimental studies was not established. In most previous studies the bone mineral density was measured only at one time point. In our study, we used the dual X-ray energy absorptiometry to measure the bone mineral density of femur, and also analysed bone metabolism markers such as osteocalcin and deoxypyridinoline (DPD) 119 Wistar-lineage twelve-month-old rats, ovariectomized (91) (high metabolism turnover type) and sham operated (28) were used. Ovariectomized rats were divided into four groups: according to the dose of elcatonin (0, 1, 5, and 25 unit (U)/kg, every other day) untreated, 1U, 5U, and 25U group. The bone mineral density and bone metabolism markers of each group were measured every month after the injection of elcatonin for three months. 25U group showed the greatest increase in bone mineral density after three months. However, poor appetite and hypokinesia were noted in this group from starting month, which decreased the bone mineral density. The bone mineral density of 1U group was slightly increased after injection during the first two months, but decreased after three months. 5U group showed slight decrease in mineral density throughout experimental periods. The levels of both osteocalcin and DPD in all groups were lower than those immediately before administration of elcatonin. Osteocalcin showed greater decrease in 5U group than in 1U group during the first two months, whereas DPD were lower in 5U group than in 1U group after three months. Osteocalcin became higher level in 5U group than in 1U group after three month. Therefore, bone mineral density continuously increased in 1U group during the first two months, and later decreased. In contrast, 5U group was prevented to decrease in bone mineral density throghout three months. In 25U group, both markers were increased one month, and DPD was markedly decreased three months after the administration of elcatonin, whereas osteocalcin showed increased levels, which indicating the largest increase in bone mineral density. Throughout the three months of experimental period, the largest increased in bone mineral density was expected in 25U group, but the decrease in bone mineral density due to side effects such as poor appetite and hypokenesia which was observed one month after starting the administration of elcatonin was a problem. Therefore, the increase in bone mineral density without inducing side effects could be expected in 1U group. It was concluded that the increase in bone mineral density could be expected safely by administering 1U/kg of elcatonin for two months.