Influences of halogenated organic substances on ovarian development and hepatic EROD activity in the three-spined stickleback, Gasterosteus aculeatus, and rainbow trout, Oncorhynchus mykiss

Abstract

Female three-spined sticklebacks were fed freeze-dried chironomids contaminated with polybrominated diphenyl ethers (PBDE) (Bromkal 70-5DE), polychlorinated naphthalenes (PCN) (Halowax 1014) and polychlorinated biphenyls (PCB) (Clophen A50) in low or high doses in the following combinations: Halowax 1014 + Clophen A50, Bromkal 70-5DE + Clophen A50, Halowax 1014 + Bromkal 70-5DE, and Halowax 1014 + Clophen A50 + Bromkal 70-5DE. The control group was fed uncontaminated freeze-dried chironomids. After 2.5 months of exposure, the fish were dissected for chemical, biochemical and morphological analyses. Hepatic cytochrome P450-dependent ethoxyresorufin- O-deethylase (EROD) activity was induced (3-to 7-fold) in all high-dose groups, but not in the low-dose groups. There were no significant differences between the control and exposed groups in liver somatic index (LSI), gonadosomatic index (GSI), progesterone 17α-hydroxylase activity or the mean proportion of atretic oocytes per total number of oocytes. The mean gonadal progesterone 6β-hydroxylase activity in the control group was 0.3 ± 0.2 pmol mg −1 protein min −1. All groups except the one that received a high dose of Halowax 1014 + Clophen A50 + Bromkal 70-5DE had significantly higher gonadal progesterone 6β-hydroxylase activities compared with the control group. The mean activities in the significantly induced groups ranged from 9.4 ± 3.3 to 20.6 ± 5.0 pmol mg −1 protein min −1. Rainbow trout yolk-sac fry were injected with the same substance blends as the sticklebacks, except that Halowax 1014 + Clophen A50 + Bromkal 70-5DE was not included in the study. Furthermore, each substance alone was injected into the fry. The substances were dissolved in dimethyl sulfoxide (DMSO), and three concentrations were prepared. Halowax 1014. Clophen A50, and Halowax 1014 + Bromkal 70-5DE significantly induced the EROD system. In conclusion, the study showed that Halowax 1014 and Clophen A50 were potent inducers of the cytochrome P450 enzyme system in fish, whereas Bromkal 70-5DE was not. Furthermore, the differences in progesterone hydroxylase activities recorded between the control and exposed groups point to the importance of future thorough studies of organohalogen influence on the hormonal cycle.