Expression of bone protein mRNA at physiological fluoride concentrations in rat osteoblast culture

Fluoride causes an increase in the amount of unmineralized osteoid. To determine whether the increase in osteoid is due to greater protein expression in the presence of fluoride, we measured the relative amount of mRNA expressed by fetal rat calvaria cells maintained in culture for either 18 or 26 days in the presence of 0, 5, 20 or 300 microM fluoride. There were no differences in the level of expression of mRNA for collagenous or non-collagenous proteins in fluoride-treated cells as compared with control cells at 18 days in culture. Expression of mRNA for osteocalcin and alpha 1-type 1 collagen was decreased at 300 microM fluoride after 26 days culture. The amount of [3H]thymidine incorporation in cells exposed to the different amounts of fluoride was measured at various time points. Fluoride did not alter the time at which rapid cell proliferation ended. These studies indicate that at physiological serum levels, fluoride does not increase expression of mRNA by osteoblasts. The relative increase in osteoid in bone may be related to other mechanisms such as altered matrix mineralization.