Changes in the kidney peroxidase activity in fish exposed to some industrial pollutants

Fish under abnormal environmental conditions suffer from retarded growth and other physiological dysfunctions related to thyroxine deficiency. In teleosts lacking a definite thyroid gland the kidney plays a very important role in biosynthesis of the thyroidal hormone, in which peroxidase has an indirect action. Effects of some industrial pollutants and factory effluents on fish kidney peroxidase activity were recorded in Ophicephalus punctatus and Clarias batrachus. At concentrations of the pollutants at which 70-100% of the fish survive the exposure, peroxidase activity was greatly inhibited, indicating that even sub-lethal doses of toxicants may cause drastic changes in the physiological systems. The peroxidase activity increased well above the control levels at 5-h and 27-h exposures in some cases, but declined towards the end of the test.