Studies on the metabolism of chlorophenols in fish. V. Isolation and identification of a conjugated phenol excreted by goldfish.

A study has been made of the isolation and identification of a conjugated PCP occurring in goldfish, Carassius auratus. The amount of PCP in the fish body was less than that lost from the PCP-medium during culture. This loss of PCP was caused, not by decomposition, but by transformation of the PCP by the fish to some bound-form which was easily hydrolyzed on heating in acidic solution to release free-PCP. Most of the PCP excreted by the fish was in a conjugated form accompanied with a small amount of free-form. Conjugated PCP excreted by goldfish into the culture medium was isolated by treating the medium with activated charcoal, followed by elution with an ammonia-acetone mixture, and finally by passing the concentrated eluate, under reduced pressure, through a Sephadex G-10 column. The isolated conjugate was identified as pentachlorophenylsulfate which was identical to that found in the short-necked clam by KOBAYASHI et al. (1970). The PCP conjugate was identified by precipitation with BaCl2, extraction with xylene, thin layer chromatography, UV-absorption spectra and the molar ratio of PCP to SO4. Glucuronide which is another typical conjugate of phenols in mammals was not detected. The present study shows that fish possess a detoxication mechanism for drugs, at least chlorophenols, which involves sulfate conjugation. This is contrary to the conclusion of BRODIE et al. (1962) that fish dispose of drugs only by passive diffusion through the gills without detoxication by conjugation or oxidation.