Metabolic fate of [1- 14C]isobutyric acid in the rat

Abstract

Isobutyric acid (IBA) has potential use as a fungistat for the storage of moist grain. Since a complete accounting of the fate of IBA has not been reported, the metabolic fate of [1- 14C]IBA was investigated. [1- 14C]IBA was administered by gavage to male Charles River CD rats at doses of 4, 40, and 400 mg/kg body weight and to female rats at 400 mg/kg. All rats showed a similar excretion pattern. [1- 14C]IBA was eliminated rapidly in the breath as expired 14CO 2. At 4 hr, 75.4, 83.3, and 66.7% of the dose was eliminated in the breath by male rats dosed with 4, 40, or 400 mg/kg, respectively. At 48 hr, 85–90% of the dose was eliminated in the breath. Urinary radioactivity averaged 3.5% of the dose, with about 2 3 of the radioactivity present as urea. Fecal radioactivity was less than 1% of the dose. The excretion of radioactivity by female rats was similar to that of male rats dosed with [1- 14C]IBA. Isobutyric acid disappeared rapidly from the plasma of rats dosed by gavage with 400 mg/kg. These studies show that IBA is rapidly metabolized to CO 2 and its use as a feed fungistat is unlikely to contribute to the endogenous levels of IBA in the flesh, eggs, or milk or grain-consuming animals.