Thidiazuron uptake, distribution and metabolism in bluegills and channel catfish1

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Abstract
Bluegills (L. macrochirus) exposed to 0.1 ppm of [14C]thidiazuron cotton defoliant for 28 days under continuous flow conditions accumulated relatively low levels of radiocarbon. The maximum detected was 5.4 ppm in filet tissue after 1 day. During a 14-day depuration period, radioactivity declined to 1.0 ppm or less. Fractionation of offal and filet tissues from bluegills collected at 28 days indicated that most of the radioactive material was water soluble, although appreciable amounts of organosoluble radioactive material also were present. When bluegills were injected i.p. with [14C]thidiazuron, metabolism and elimination were relatively rapid. Organosoluble radioactive material isolated from fish tissue included thidiazuron, its 2-hydroxyphenyl derivative, phenylurea and several unknowns. Channel catfish (I. punctatus) exposed under static conditions to a system containing 0.15 ppm [14C]thidiazuron incorporated into soil also accumulated only low concentrations of radiocarbon. The maximum detected was 2.5 ppb in offal tissue at 7 days. In filet tissue, radioactivity did not exceed 0.5 ppb. There was no evidence from these studies to indicate that thidiazuron would pose a hazard to the aquatic ecosystem.