Histomorphometric Change of Bone and Metabolic Marker Expression in Rats Induced by Chronic Fluorosis

Objectives  In order to investigate the patho-morphological change in the bone tissue of rats caused by chronic fluorosis and the change of metabolic marker of bone injury related to fluorosis.

Methods  Forty eight healthy SD rats were randomly divided into 4 groups, including a control group and 3 fluoride treated groups, the concentration of sodium fluoride in their drinking water was 0 mg/L, 50 mg/L, 150 mg/L and 250 mg/L, respectively. After six months of exposure to fluoride, the incidence of dental fluorosis and the content of fluoride in urine, bone and blood were detected by fluoride ion selective electrode method. The femoral metaphysis of rat was stained with hematoxylin eosin (HE) and observed under optical microscope. The levels of bone metabolic marker in serum were determined by enzyme-linked immunosorbent assay(ELISA).

Results  The gain of body weight was less in fluoride treated groups than that in the control group except in the high fluoride female group. The incidence of dental fluorosis and the level of fluoride in urine, bone and blood in treated groups were higher than those in the control group (P<0.05), the degree of dental fluorosis was correlated with the increase of fluoride in drinking water and the extension of experimental time. The cortical thickness of femur bone in medium and high fluoride group was higher than that of control group (P<0.05). The trabecular area in medium and high fluoride group was higher than that of the control group(P<0.05), but the trabecular area in low fluoride group was less than the control group (P<0.05); The number of osteoblasts in cortical bone of 3 treated groups were lower than that of the control group(P<0.05). Compared with the control group, the level of BALP, BGP and PⅠNP in 3 treated groups were less than that of the control group (P<0.05); and the level of CTX-Ⅰand TRACP-5b in most of treated groups were less than the control group (P<0.05).

Conclusions  After fluoride being added into drinking water for 6 months, the metabolic indexes reflecting the activity of osteoblast and osteoclast were down-regulated. The bone mass of rats exposure to 150 mg/L and 250 mg/L NaF in drinking water was increased, while those exposure to 50 mg/L NaF was decreased under histomorphometric examination. It suggested that fluoride exert an impact on the activity of osteoblast and osteoclast, and the effect was related to the dosage of. fluoride.