Impact of polychlorinated naphthalenes (PCNs) in juvenile Baltic salmon, Salmo salar: Evaluation of estrogenic effects, development, and CYP1A induction

Juvenile Baltic salmon, Salmo saint; were fed commercial salmon food contam inated with different concentrations of polychlorinated naphthalenes (PCNs; 0.1, 1, 2, or 10 mu g PCN/g food). Among other effects, possible estrogeni c impact caused by PCNs were evaluated. Fish were therefore fed a diet cont aminated with 17 beta-estradiol (E2; 0.94 or 9.4 mu g E2/g food), as a posi tive control. After 8, 13, 17, and 41 weeks, sampling took place. Growth, L iver somatic index (LSI), EROD activity, and vitellogenin content in blood plasma were measured along with morphological studies of gonads and chemica l analyses to determine the effects caused by PCNs. Exposure to PCNs did no t seem to have any effects on body weight gain, since the group fed the hig h dose followed the growth in the control group during the entirely experim ental period. After 41 weeks of exposure the groups fed 2 and 10 mu g PCN/g food had significantly lower LSIs compared with the control, indicating li ver toxic effects of PCNs. Furthermore, a dose-dependent induction of EROD activity was found. At week 41, the control group had an activity of 4.9 +/ - 4.8 pmol/mg prot/min, whereas it was between 69 +/- 21 and 720 +/- 320 pm ol/mg prot/min in the exposed groups, respectively. Examination of gonadal morphology showed that PCNs also had negative effects on ovaries in Baltic salmon, including delayed development. The distribution between females and males, gonadal morphology, and vitellogenin content in blood plasma did, h owever, indicate that PCNs are not capable of causing effects similar to E2 or xenoestrogens. Exposure to both of the concentrations of E2 resulted in decreased body weight gain, increased LSI, and feminization of the gonads. E2 did, however, not induce any EROD activity.