BONE HISTOMORPHOMETRIC CHANGES DUE TO DIFFERENCES IN CALCIUM INTAKE UNDER METABOLIC-ACIDOSIS IN RATS

Effects of differences in calcium (Ca) intake on bone metabolism under metabolic acidosis were examined by bone histomorphometry in rats. Ra ts were divided into 5 diets; low Ca (0.02%) diet (LCD), moderate low Ca (0.3%) diet (LmCD), standard Ca (O.62%) diet (SCD), moderate high C a (1%) diet (HmCD) and high Ca (3%) diet (HCD). Each diet rats were su bdivided into the acidotic group given a 1.8% ammonium chloride soluti on as drinking water and control group given deionized water. Blood an d double labeled bone were collected 30 days later. Arterial blood pH was significantly lower, and plasma ionized Ca level and urinary Ca ex cretion were higher in the acidotic groups than those in the control g roups in all diets. Breaking force in femur and bone volume in tibial proximal metaphysis were significantly lower in the acidotic groups th an those in the control groups in LCD, LmCD and SCD. In the acidotic g roups, osteoid thickness was significantly higher in LCD than that in LmCD, HmCD and HCD. Mineral apposition rate in the acidotic groups was significantly higher in LCD and LmCD than that in HmCD and HCD. These results suggest that bone mineral loss and bone fragility under metab olic acidosis may be accelerated by high turnover of bone metabolism d ue to insufficient dietary Ca intake, but can be prevented by adequate supplementation of Ca.