Subchronic toxicity study of L-isoleucine in F344 rats

A subchronic toxicity study with L-isoleucine was conducted using F344 rats. Groups of 10 rats of each sex were given diet containing 0, 1.25, 2.5, 5.0, or 8.0% L-isoleucine for 13 wk. No treatment-related effects were observed in terms of body weight change, food consumption or hematology. In both sexes given 8.0% L-isoleucine, increased or a tendency for increased urine volume and relative kidney weights were observed. Furthermore, the high-dose L-isoleucine treatment brought about an elevation of urinary pH and variations in serum electrolytes. However, histopathological alterations related to these changes were not observed in any organs of either sex. In conclusion, the present study demonstrated that L-isoleucine possessed minimal toxicity at dietary levels of 5.0% and 8.0%, while it did not exert any adverse affects at a dietary level of 2.5% or less.