The urinary and biliary excretion, tissue distribution and metabolism of 14C-labelled 2,4-dichloro- or 2,4,5-trichloro-phenoxyacetic acids (2,4-D or 2,4,5-T) were measured in dogfish sharks, Squalus acanthias. 2. Both herbicides are extensively metabolized (greater than 90%) to the corresponding taurine conjugates, and are excreted predominantly via the urine, where ca. 70% of the administered dose appears within 4-6 days after treatment. 3. The highest tissue levels of 2,4-D or 2,4,5-T were found in liver and kidney. Penetration of both herbicides into the CNS was restricted. 4. Plasma elimination was rapid and the 0.5 for either phenoxyacetic acid was less than 45 min. Similarly, rapid clearance as seen from renal tissue. Final t0.5 values for muscle were about 2-3 days while the major organ showing 2,4-D or 2,4,5-T retention was the liver, where t0.5 values were about 5 days for both the herbicides. 5. The overall pharmacokinetics in the dogfish shark for these herbicides resembled those seen in some mammals.
