Nail and bone surface as indicators of acute exposure to fluoride in rats.

This study evaluated the use of nails and bone surfaces as indicators of acute exposure to fluoride in rats. Six groups (n=10/grp), aged 70 days, received, by gastrogavage, single doses of sodium fluoride containing 10, 35, 45, 60, 75 and 90 mg fluoride/kg body weight. The control group received deionized water. Two hours after fluoride administration, the rats were killed and their plasma, nails (halves near to the growth end) and femur were collected. Nail and plasma fluoride concentrations were analyzed with the electrode following HMDS-facilitated diffusion. Femur surface fluoride was removed from a circular area (4.52 mm²) by immersion in 0.5M HCl for 15 seconds, buffered with TISAB and analyzed with the electrode. Data were analyzed by ANOVA and Tukey's test (p<0.05) and by linear regression (p<0.001). Average fluoride concentrations ranged from 55.4 to 91.5 mg/g for nails; from 0.019 to 6.937 mg/mL for plasma and from 617 to 2,394 mg/g for femur surface. Fluoride concentrations in nails from experimental groups were not different from control. Regarding plasma fluoride, all experimental groups differed from control, except the group that received the lowest dose. In respect to femur surface fluoride, only the group that received the highest dose differed from control. A strong correlation was found between plasma fluoride and the dose administered (r=0.736) and a medium correlation was found between femur surface and the dose administered (r=0.510). Data suggest that two hours after an acute fluoride administration, nails and femur surface are not good indicators of fluoride exposure.