Renal Clearance of Fluoride.

Abstract

Fluoride in dog plasma was completely ultrafilterable through visking membranes when tested using the centrifuge type apparatus. In dogs with a normal water load, the average normal renal fluoride clearance was 2.7 ml/min.; the fluoride : chloride clearance ratio, 19; and the fluoride : creatin-ine clearance ratio, 0.077. Fluoride clearance was more rapid than that of simultaneously measured sodium or chloride clearances or urine flow. During mannitol diuresis, fluoride was cleared at a rate higher than that of sodium, chloride, or phosphate. Fluoride clearance, although greater than urinary flow, varied directly with the flow under mannitol osmotic diuresis. Intravenous infusion of hy-pertonic NaNO3 or Na2SO4 solutions, creating a salt diuresis, did not affect fluoride excretion. Hypertonic NaCl infusion did increase the fluoride clearance. Although fluoride : creatinine clearance ratios were raised greatly by intravenous fluoride, the highest ratios were attained during fluoride infusion plus osmotic diuresis with hypertonic mannitol or NaCl. No evidence for a tubular secretion of fluoride was obtained.