CHRONIC FLUORIDE EXPOSURE DOES NOT CAUSE DETRIMENTAL, EXTRASKELETAL EFFECTS IN NUTRITIONALLY DEFICIENT RATS

On the basis of observations that endemic fluorosis occurs more often in malnourished populations, a series of studies tested the hypothesis that deficient dietary intake of calcium, protein or energy affects f luoride metabolism so that the margin of safe fluoride exposure may be reduced. The objective of the investigation was to determine whether changes in fluoride metabolism in nutritionally deficient rats resulte d in manifestation of any extraskeletal toxic fluoride effects not obs erved in healthy animals. This investigation included two studies, one that monitored the effect of calcium deficiency on the effects of chr onic fluoride exposure, and a second study that observed fluoride effe cts in rats that were deficient either in protein or in energy and tot al nutrient intake. Control and experimental rats received drinking wa ter containing 0, 0.26 (5), 0.79 (15) or 2.63 (50) mmol fluoride/L (mg /L) for 16 or 48 wk, Control rats were fed optimal diets and experimen tal rats were fed diets deficient in calcium (Study 1) or protein (Stu dy 2). An additional group of experimental rats (Study 2) was provided with a restricted amount of diet; thus these rats were deficient in e nergy and total nutrient intake, The intake, excretion and retention o f fluoride were monitored; after the rats were killed, tissue fluoride levels and biochemical markers of tissue function were analyzed. Bone marrow cells were harvested from some of the rats, after 48 wk of tre atment, for determining the frequency of sister chromatid exchange, a marker of genetic damage. Although there were significant differences among fluoride treatment groups in fluoride excretion and retention th at resulted in significantly greater fluoride levels in tissues of the experimental rats, we were unable to detect any harmful, extraskeleta l biochemical, physiologic or genetic effects of fluoride in the nutri tionally deficient rats.