AbstractThe distribution of fluoride and chloride in muscle, liver, and tendon was studied in groups of 6-15 rats sacrificed at 80-240 min after intraperitoneal injections containing radiofluoride (18F) and radiochloride (36Cl). Liver exhibited a constant 18F(tissue water):18F(plasma water) ratio over 120-220 min and this ratio was constant in muscle over 80-120 min. The 18Ftw/18Fpw ratios for muscle were lower than those of liver. The ratios of 18F distribution for both liver and muscle declined significantly at the longest time periods probably as a result of reductions of intracellular pH and/or increases of extracellular pH. Chloride space volumes were determined from chloride analyses of the tissues and plasma and confirmed by the 36Cl(tissue water):36Cl(plasma water) ratios. The fluid space volumes and the 18F(tissue water):18F(plasma water) ratios were used to indicate that the average intracellular ionic fluoride concentrations of liver and muscle are, respectively, 79 and 38% that of plasma water...