Baseline estrogenic activity in juvenile brown trout liver and primary hepatocytes: integrated molecular and immunohistochemical analysis

Characterization of sex and biometry of fish donors for primary cell culture is often overlooked. Consequently, the influence of donor biological variability—such as reproductive status—on basal estrogenic expression in fish hepatocytes remains underexplored in toxicological studies. This study examines whether inherent differences among 1-year-old juvenile brown trout (Salmo trutta) are reflected in estrogenic signatures in liver tissue and the corresponding primary hepatocyte cultures from the same individuals. To our knowledge, no previous research has systematically assessed interindividual variation in estrogenic markers in brown trout primary hepatocytes. To address this, we evaluated the gene and protein expression of four classical estrogenic targets: vitellogenin, zona pellucida protein, estrogen receptor alpha, and estrogen receptor beta. No statistically significant differences in basal expression levels were observed across male and female donors in either hepatocytes or liver tissue. Nonetheless, interindividual variability was evident, reflecting natural biological differences in gonadal development and physiological status. The findings highlight the need to document and control donor sex, reproductive status, and individual variability when selecting fish for hepatocyte culture, even when sex differences in basal expression are not statistically significant, thereby providing a crucial baseline for toxicological experiments using primary trout hepatocytes.