ABSORPTION, TISSUE DISTRIBUTION AND METABOLISM OF CHLORPYRIFOS IN CHANNEL CATFISH FOLLOWING WATERBORNE EXPOSURE

The pharmacokinetics, tissue distribution, and metabolism of waterborn e chlorpyrifos were investigated in channel catfish (Ictalurus punctat us) fitted with arterial and urinary catheters. Pharmacokinetic analys is indicated rapid absorption of parent chlorpyrifos from water into b lood and slower distribution to peripheral tissues. Total C-14 residue concentrations were highest in fat and lowest in muscle. Parent chlor pyrifos comprised >90% of the total C-14 residues in the whole fish. C -14 residues were excreted by renal and biliary routes as metabolites of chlorpyrifos; excretion of the parent chemical was negligible. Tric hloropyridinol (TCP) was the major metabolite in blood (approximately 40% of total residues), whereas the glucuronide conjugate of TCP was t he major metabolite in urine (60-90%) and bile (>90%). The pharmacokin etics and metabolism of waterborne chlorpyrifos in the channel catfish were similar to the disposition of chlorpyrifos in other vertebrates.