Alterations of Lactate Dehydrogenase Activity in the Skeletal Muscles and Cardiac Tissue of Salmonid After Disinfecting Procedure With Chloramine-T

Abstract

Chloramine-T is a widely used disinfectant for the treatment of gill diseases of fish in freshwater and can be toxic to fish. Therefore, the current study aimed to examine the safety of this disinfecting product (as it has been attracting researchers’ attention for applying in aquatic animals) for fish health using markers of aerobic and anaerobic capacity (i.e. lactate dehydrogenase activity) in the skeletal muscle and cardiac tissues of rainbow trout (Oncorhynchus mykiss Walbaum), grayling (Thymallus thymallus Linck), and brown trout (Salmo trutta m. fario). Twenty-two clinically healthy rainbow trout, twenty-one brown trout, and twenty graylings were exposed to Chloramine-T in a final concentration of 9 mg per L. The Control group of fish was handled in the same way as the exposed groups. Fish were bathed for 20 min and repeated three times every 3 days. Two days after the last bathing fish were sampled. In the skeletal muscle tissue, LDH activity was decreased in the rainbow trout and grayling after disinfection by Chloramine-T compared to the unhandled controls. On the other hand, LDH activity was increased in the skeletal muscle tissue of brown trout. In the cardiac tissue, disinfection by Chloramine-T caused the decrease of LDH activity in rainbow trout, brown trout, and grayling. Moreover, in unhandled controls, LDH activity in the cardiac tissue was higher by 107.5% (p = 0.000) in brown trout and by 57.6% (p = 0.001) in the grayling compared to the values obtained in skeletal muscles. The present investigation demonstrates the alterations in LDH activity in the skeletal muscles and cardiac tissue after the disinfecting procedure with Chloramine-T in dose 9 mg per L. Although, after disinfection, the rainbow trout, brown trout, and grayling showed decreased trends of aerobic responses in the cardiac tissue indicating adaptive response against the Chloramine-T toxicity. Similar trends were observed in the skeletal muscles of rainbow trout and grayling. On the other hand, LDH activity in the skeletal muscles of brown trout after the disinfecting procedure with Chloramine-T was increased. Therefore, these biochemical parameters can be considered as indicators for the assessment of disinfecting effects, although further studies are required for investigating the mechanism involved in this pattern.