Perinatal and postnatal exposure to 4-tert-octylphenol inhibits cortical bone growth in width at the diaphysis in female mice

The aim of this study was to investigate the effects of 4-tert-octylphenol (OP) on bone growth in vivo. Pregnant mice were exposed to drinking water containing either 1 μg/ml OP (LD group) or 10 μg/ml OP (HD group) from gestational day 10 and throughout the lactation period. After weaning, the pups were allowed free access to drinking water containing the appropriate OP concentrations. The serum osteocalcin level of the females, but not the males, was significantly lower in the LD and HD groups than in the control group on postnatal day 31. The femurs of the females were analyzed by peripheral quantitative computed tomography and immunohistochemistry for alkaline phosphatase (ALP) was performed in the sections of the formalin-fixed femurs. The periosteal and endosteal circumferences of the cortical bone at the diaphysis were significantly smaller in the LD group, but not the HD group, than in the control group (4% and 6% smaller, respectively), while there were no differences in the cortical bone density, cortical bone area, or cortical thickness among the three groups. There were fewer ALP-positive cells on the periosteal surfaces at the diaphysis in the LD group than in the control group. The values of the strength strain index (xSSI, ySSI, and pSSI) decreased with decreasing the periosteal circumference. In conclusion, the exposure of female mice to OP during the perinatal and postnatal periods inhibited the periosteal bone formation in the cortical bone at the diaphysis of the femur, thereby causing a reduction in bone growth in width.