Absorption, distribution, and elimination of a single oral dose of [14C]tri-o-cresyl phosphate in hens.

The absorption, distribution, elimination, and metabolism of a single oral dose of 50 mg (4.6 microCi)/kg of uniformly phenyl-labeled [14C]tri-o-cresyl phosphate (TOCP) was investigated in adult chickens. Three treated hens were killed at each time interval: 0.5, 1, 2, and 5 days. TOCP was absorbed from the gastrointestinal tract and subsequently distributed throughout the body. Generally, the highest concentrations of radioactivity were associated with gastrointestinal tract parts, bile, kidneys, liver, and lungs. Most of the radioactivity (47%) was excreted in the combined fecal-urinary excreta during the first 12 h. Very small fractions of the dose were deposited in egg albumen and egg yolk, 0.12% and 0.24%, respectively during the 5-day study. After 5 days, 99% of the dose was eliminated in excreta. TOCP and its metabolites in bile and the combined fecal-urinary excreta were analyzed by high-performance liquid chromatography and liquid scintillation spectrometry. TOCP and nine of its metabolites were identified. In the bile a TOCP active metabolite, saligenin cyclic-o-cresyl phosphate, was the predominant compound found compared to the parent compound in the excreta. These results suggest that in the hen TOCP is excreted slower than the rat and also undergoes metabolic activation. The absorption, elimination, and metabolic profile of TOCP in the hen may contribute to its sensitivity to delayed neurotoxicity.