Abstract
Human activity has spread trace amounts of chemically stable endocrine-disrupting pollutants throughout the biosphere. These compounds have generated a background level of estrogenic activity that needs to be assessed. Fish are adequate sentinels for feminization effects as male specimens are more sensitive than humans to exogenous estrogenic compounds. High mountain lakes, the most distant environments of continental areas, only receive semi-volatile compounds from atmospheric deposition. We analyzed the expression levels of estrogen-regulated genes in male fish from these mountain lakes in Europe. Incipient feminization involving expression of estrogen receptor and zona radiata genes revealed a widespread diffuse estrogenic impact. This effect was correlated with the concentrations of some organochlorine compounds in fish and was consistent with the persistent occurrence of these tropospheric pollutants in the most remote planet regions. These results should be of general concern given the increasing endocrine disruption effects in human populations.
Highlights
Purposes, the mRNA expression for cytochrome P450 1A (Cyp 1A) that records the ectopic activation of the receptor of dioxin-like compounds[16,17] has been measured
Total RNA isolated from different liver Salmo trutta (39 males and 61 females) collected in lakes from two mutually distant European mountain ranges, the Tatras and the Pyrenees[16] (Supplementary Table S1) were retrotranscribed and used as template in a standard PCR using appropriate oligonucleotide pairs to detect Vtg, Zrp and ERα (Estrogen Receptor α ) mRNA in liver
The treatment increased hepatic mRNA levels for the three genes, corresponding the strongest induction to the Vtg gene and the lowest one to ERa. These results indicate that the three genes can be used to monitor the exposure of S. trutta to estrogens
Summary
Fish (S. trutta, brown trout) were sampled by net fishing. Ten brown trout juveniles (mean body weight 11.4 ± 2 .6) were treated with a single dose intraperitoneal injection of estradiol (1 mg/kg) and kept for 48 h. They were sacrificed by neck dislocation and liver samples stored in RNAlater. The extracts were cleaned up with sulfuric acid (5 times), concentrated by vacuum rotatory evaporation and to near dryness under a gentle nitrogen flow. They were redissolved in isooctane (50 μ l). Principal Component Analyses were performed after logarithmic transformations of mRNA abundances and chemical concentrations
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