Atlantic Salmon (Salmo salar) GILL Primary Cell Culture Oxidative Stress and Cellular Damage Response Challenged with Oxytetracycline Antibiotic

Salmon farming has been affected by various bacterial diseases, and the use of antibiotics (such as oxytetracycline "OTC") to control these diseases has become necessary and thus routine. This study aimed to determine how the gill cells are affected by OTC in <i>Salmo salar</i>. Gill tissue culture was performed in periods of 0.5, 1, 3, 6, 12, and 24 h, assessing the enzymatic activity and mRNA expression of catalase (CAT), cytochrome p450, glutathione peroxidase (GPx), glutathione reductase (Gr), and superoxide dismutase (SOD), HSP70 and HSP90, in response to two doses of OTC: 0.25 (low), and 3 µL/mL (high). The results indicated that the enzymatic activity of SOD and CAT showed low enzyme activity at both doses. At the same time, GR presented varied response patterns depending on the time and dose of OTC used, contrary to GPx, which just increased the enzyme activity at early times. Although the mRNA expression presented the most precise pattern of expression, they were not in line with the enzymatic activities. The HSP70 and HSP90 mRNA expression response (as a cellular damage marker) increased mRNA levels at low and high doses, respectively, but at different times, alluding to a differentiated response given by the size of the chaperone. These results suggest an oxidative response of the gills to OTC exposure and constitute significant information on the amount of OTC used in aquaculture and on methods for improving the optimal dose of drugs, fish health, and, consequently, environmental health.