Metabolism of orally administered naphthalene in spawning English sole ( Parophrys vetulus)

Abstract

English sole (gravid females and ripe males) were force-fed [ 3H]naphthalene (NPH) in salmon oil and tissues were examined at 24, 48, and 168 hr. NPH was detected in all tissues and fluids examined (e.g., liver, blood, muscle, bile, testes, and ovaries) at 24 hr. There were no statistically significant differences in NPH concentrations, based on dry weight, between comparable tissues and fluids of the sexes, except for the gonads. Ovarian NPH concentrations were approximately three times higher than those in testes. The highest percentage (5%) of the total dose at 24 hr was present in the ovaries; liver and muscle contained about 1–2% of the dose. Concentrations of NPH in all tissues declined markedly from 24 to 168 hr. At 24 hr, male English sole had significantly higher hepatic NPH hydroxylase activity than did female sole. However, no significant sex differences were evident in tissue concentrations of total metabolites of NPH. In liver, blood, and testes, the metabolites at 24 hr were composed of approximately equal proportions of conjugates and nonconjugates. Nonconjugates were the predominant metabolites in the ovaries (>88% of the total). Thin-layer chromatography (TLC) of metabolites from liver, blood, ovaries, and testes revealed that the major nonconjugate metabolite was 1,2-dihydro-1,2-dihydroxynaphthalene (diol) and glucuronides were the major conjugate class present. Both TLC and high-performance liquid chromatography indicated that the glucuronide conjugate in the liver was derived from the diol. The naphthol conjugates were not detected. The ability of fish to rapidly accumulate orally administered NPH and its metabolites in the gonads may have significant implications with respect to fertilization and subsequent development of the embryo.