Abstract

Aquaculture is currently the fastest-growing sector in animal production, with an average annual growth rate of 7.5% since 1970. In Chile, the industry is largely driven by salmonid farming, with Salmo salar (Atlantic salmon) accounting for over 65% of national production. This species has shown the most significant growth within the sector. This growth is achieved by having high-density farming, which results in high levels of stress due to overcrowding and the appearance of pathogens such as the Infectious Salmon Anemia (ISA) virus, Bacterial Kidney Disease (BKD), Caligus sea lice (Caligus rogercresseyi), and Piscirickettsiosis (SRS) caused by Piscirickettsia salmonis, among others. This study evaluated the toxicity of the two most commonly used antibiotics in the salmon industry-oxytetracycline and florfenicol-at four concentrations each, using primary liver cell cultures of Atlantic salmon (Salmo salar). Oxidative stress was assessed through enzymatic activity and gene expression of oxidative markers, including cytochrome P450, catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx). Samples were analyzed at 1, 3, 6, 12, and 48 h post-exposure. These findings reveal time- and dose-dependent oxidative responses in salmon liver cells to OTC and FLO, providing critical insights into the sublethal cellular effects of antibiotics commonly used in aquaculture, which indicates the presence of a high amount of free radicals in the liver cells, indicating toxicity of both antibiotics.