Distribution and elimination of the herbicide propanil in the channel catfish (Ictalurus punctatus)

1. The uptake, elimination and tissue distribution of total radioactivity derived from the herbicide, [14C]propanil (3,4-dichloropropionanilide) and its metabolites were examined in individual farm-raised Channel Catfish which were exposed for 24 h to water containing 1 ppm of 14C-propanil under static conditions. Uptake and elimination of total radioactivity was monitored in individual animals over time in respective exposure (24 h) and depurating (144 h) aquaria. 2. Maximal uptake was reached between 8 and 12 h with approx. 38% of the absorbed radioactivity remaining in the animal after 144 h of depuration. Whole body depuration of radioactivity was biphasic with alpha and beta half-lives of 20 and 444 h, respectively. 3. Tissue distribution of total radioactivity was monitored at various time points in 12 tissues and bile over 48 h. Intestine, abdominal fat and liver possessed the greatest levels of radioactivity per gram of tissue over time. Radiolabel was shown to slowly increase in bile and intestine indicating biliary excretion as a possible pathway of metabolite elimination. 4. Bile possessed approx. 104 nmol (23%) of the remaining radioactivity in fish after 48 h. Other whole tissues possessing > 10% of radiolabel after 48 h were blood (83.5 nmol, 19% of the administered dose) and muscle (190 nmol, 43%).