Effect of long-term administration of sodium fluoride on plasma calcium level in relation to intestinal absorption and urinary excretion in rabbits.

The present study was undertaken to determine the effect of chronic fluoride toxicity on calcium metabolism. Rabbits (n = 10) were orally administered an aqueous solution of 10 mg NaF/kg body wt daily for 18 months. Equal numbers (n = 10) of age-, sex- and weight-matched rabbits kept under identical laboratory conditions, but not treated, with NaF solution, served as control. The fasting plasma calcium concentrations of fluoride-treated rabbits were significantly lower (P < 0.001) than those of control animals. In contrast to the decrease in plasma calcium level, and increase in intestinal radioactive calcium (45Ca) absorption was observed (P < 0.001) in all fluoride-treated animals. However, urinary calcium excretion levels were found to be reduced (P = not significant) in fluoride-treated rabbits. It is therefore concluded that long-term fluoride poisoning alters the calcium homeostatic mechanism, thereby affecting calcium metabolism.