Background. Some heavy metals are essential to living organisms but their excess can disturb the homeostasis of an animal. The aim of the study was to assess effects of nickel compounds on carp, Cyprinus carpio L., and to follow the toxicodynamics of this metal elimination from intoxicated fish once they were transferred to a clean ambience. Materials and methods. Individuals of carp, Cyprinus carpio L. were given a single intraperitoneal injection of a sub-lethal nickel nitrate dose (60 μg Ni ּkg-1 body weight) to assess their detoxification potential following transfer to uncontaminated habitat. The 60-day experiment was divided into 8 stages during which various organs and tissues of the fish (liver, kidneys, skin, gills, alimentary tract, muscles) were examined and subjected to assays for nickel contents at pre-set times. Nickel was determined with inductively coupling plasma atomic emission spectrometry (ICP-AES) in a JY-24 Jobin Yvon apparatus after wet digestion in concentrated HNO3 in CEM MDS 2000 microwave oven. Results. The fish intoxicated with Ni shown some behavioural changes; they were sluggish and stay near the bottom of a tank, their responses to light and sound were much slower than those of the control fish. The nickel level was observed to change with time: after initial nickel accumulation in the tissues, the metal was eliminated. The experiment highlighted changes in the intoxicated carp system during the process of detoxification. The highest biological half-life (t1/2) of nickel was recorded in alimentary tract (10 days), the lowest being typical of the liver (1.8 days). Conclusion. During detoxification, nickel was observed to be redistributed among the examined organs. Its elimination rate was depended on organ and varied from 0.003 to 0.008 µgּday-1. A long-term effect of sub-lethal intoxication was an about 5 % reduction of the fish body weight. This study has been financially supported by the State Committee for Scientific Research (KBN) (grant No. 3 PO4E 030 22).

fish intoxication, carp, Cyprinus carpio, nickel, elimination, dynamics