Changes in copper load in hepatocytes of Ohrid trout in relation to the ovarian maturation cycle

Abstract

The main aim of this study was to histochemically estimate the relative copper content in the liver during the breeding cycle of female Ohrid trout, a wild population endemic to the Ohrid Lake. The histology of the oogenetic cycle in this species was documented for the first time. Histochemistry with semi-quantification revealed positive correlations between the gonadosomatic indices and copper load. Uptake of the metal increases in the liver as the ovaries increase in size, with the highest hepatic copper load occurring postspawning. The plasmatic levels of 17β-oestradiol were also quantified, but no correlations to copper load were found, so there is no direct estrogenic control on the uptake and release of copper from the bloodstream to either organ. Therefore, when interpreting field studies or assays on hepatic copper pollution and toxicity, breeding-related seasonal changes in Ohrid trout must be taken into account.