TOXICOLOGICAL EFFECTS OF OXYTETRACYCLINE ON COMMON CARP, CYPRINUS CARPIO
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Date
2022
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KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR
Abstract
Oxytetracycline (OTC), an antibacterial agent, is extensively used in aquaculture practices all over the world. Tetracycline class of antibiotics alone were marketed to the maximum extent of 39,74,179 kg in 2019 which is about 66% of the medically important drug. Despite of its use, the toxicity of OTC to freshwater fish has been investigated. In this study, Common carp (Cyprinus carpio) were exposed to different concentrations (25, 50, 75, and 100 mg kg−1 diet) of OTC for a period of 60 days, during which fish were killed at the end of every 15 days to analyse certain haematological, enzymological and histological parameters. During the exposure period, a mixed trend was observed in haemoglobin (Hb), haematocrit, mean cell volume, mean cellular Hb, and mean cellular Hb concentration, whereas decreased red blood cell countand increased white blood cell, haemoglobin, haematocrit, mean cell volume, mean cellular Hb, mean cellular Hb concentrationwas noticed. Enzymes such as Aspartate aminotransferase, Alanine aminotransferaseand Lactate dehydrogenase that are metabolically important were studied in order to know alterations in any carbohydrate or protein metabolism due to chronic toxicant exposure. A biphasic trend was observed in the enzymatic levels of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase in the vital organs (gill, liver and muscle) of fish. In gill, activities of AST and LDH increased but that of ALT decreased. Thus enzyme activity is based on organ sensitivity to toxicant and rate of disturbances in carbohydrate metabolism. Along with haematological and enzymatic changes severe histological changes in the gills and liver were observed in fish treated with oxytetracycline. Histological investigations have long been recognized to be reliable biomarkers of stress in fish.
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Furthermore, the observed histological alterations appear to be result of several physio-metabolic disordersconsequence of the biochemical and molecular modes of action of OTC. The alterations of these parameters lead to the conclusion that these parameters may be used as biomarkers in monitoring OTC toxicity in aquatic environment. KEYWORDS: Oxytetracycline, Cyprinus carpio, Haematology, Enzyme, Histology