Evidence for endocrine disruption in perch (Perca fluviatilis) and roach (Rutilus rutilus) in a remote Swedish lake in the vicinity of a public refuse dump.

A two-year study on perch (Perca fluviatilis) in Lake Molnbyggen, Sweden, located in a pristine area but with a public refuse dump in the vicinity, has been conducted. The mechanistic approach through a set of biomarkers during the first year included age, condition, somatic growth, liver, gonad, and spleen weights, and a number of other physiological variables, in addition to ethoxyresorufin O-deethylase, glutathione-S-transferase, glutathione reductase, catalase, and the formation of DNA adducts in the liver. Perch from the uncontaminated Lake Djursjön, located in a neighboring drainage area, were used as reference fish. The most pronounced effect was a 80% reduction in the gonadosomatic index (GSI) for females and a corresponding 36% reduction in males. Fin erosion and shallow open sores were also frequently observed. Biomarkers and later chemical analysis employed indicated that exposure to well-known environmental pollutants was low, suggesting that less well-known antrophogenic substances are responsible for the effects observed in perch from Lake Molnbyggen. During the second year, roach (Rutilus rutilus) of both sexes were also included in this study. In addition, aromatase (P450arom) activity in the brain and testosterone and 17beta-estradiol levels in blood plasma were analyzed. Only one-fourth of the female perch were found to be sexually mature, which was associated with decreased GSI, lower P450arom activity, and reduced circulating levels of steroids. The reproductive disorders observed indicates disturbed endocrine function(s), arresting the majority of the female perch in a sexually nonreproducible immature stage. This novel study is the first to report evidence for endocrine disruption in wild populations of fish living in a lake exposed to leakage water from a public refuse dump.

Hepatic activities of thiamine-dependent enzymes, glucose-6-phosphate dehydrogenase and cytochrome P4501A in Baltic salmon (Salmo salar) yolk-sac fry after thiamine treatment.

Sea-run Baltic salmon (Salmo salar) populations have been affected by the M74 syndrome since 1974 causing high yolk-sac fry losses in Swedish compensatory rearing plants. M74 has been shown to be a maternally transmitted thiamine (vitamin B(1)) deficiency. The aim of this study was to investigate possible relationships between thiamine and hepatic activities of the thiamine-dependent enzymes transketolase (TK) and alpha-ketoglutarate dehydrogenase (alpha-KGDH) in addition to glucose-6-phosphate dehydrogenase (G6PDH) and cytochrome P4501A (CYP1A), measured as 7-ethoxyresorufin O-deethylase (EROD), in Baltic salmon yolk-sac fry after treatment with thiamine. Thiamine concentrations and activities of TK, alpha-KGDH and EROD were significantly lower (P<0.05) in M74 groups compared to controls (not developing M74) and family groups of thiamine injected females. In M74-developing groups the thiamine immersions reduced the mortality from 86 to 13% and restored thiamine concentrations and activities of TK, alpha-KGDH and EROD to levels slightly lower than the immersed controls. An interesting fact was that the controls showed significantly elevated (P<0.05) TK and alpha-KGDH-activities after immersions in thiamine, indicating that they also may have a stressed thiamine metabolism. The TK and alpha-KGDH-activities of unimmersed groups correlated significantly (P<0.05) with the thiamine content. We suggest that the low activities of TK and alpha-KGDH in M74 groups may be an integrative part in the pathogenesis of M74 development.