Beňova K. , M. Toropi la , M. Fal is , p. Dvořak: Influence of Ionising Radiation on the Activity of Selected Adaptive Enzymes in Chickens and Rats. acta vet. Brno 2003, 72:201-205. The effects of ionising radiation on the activity of two adaptive enzymes in the serum of poultry and laboratory rats were investigated. Chickens were divided into three groups. Those aged 28 days were gamma-irradiated with either a single whole-body dose of 2.0 Gy (output 0.27 Gy/min) (group 1, n = 6), or a single whole-body dose of 4.5 Gy (output 0.33 Gy/min) (group 2, n = 6). rats and chickens (group 3, n = 6) aged 37 days were exposed to a single whole-body dose of 5.0 Gy (output 0.27 Gy/min). analyses were carried out at 6, 24 and 48 h after irradiation. Chickens irradiated with the 2.0 Gy dose showed a significant decrease in the activity of alT at 6, 24 and 48 h after irradiation compared to controls. Chickens irradiated with the 4.5 Gy and 5.0 Gy dose showed a significant decrease at 6 and 24 h after irradiation. rats irradiated with the 5.0 Gy dose showed a significant decrease in the activity of alT at 24 and 48 h after irradation compared to controls. The activity of aspartate aminotransferase was increased in all observation periods in chickens from the group irradiated with 2.0 Gy. The chickens irradiated with 4.5 Gy showed a decrease in this parameter, significant (p < 0.05) at 6 and 48 h after irradiation. The activity of asT in chickens irradiated with 5.0 Gy was increased in all periods of investigation. a non-significant decrease in the activity of asT was detected in rats irradiated with 5.0 Gy in all periods of observation compared to controls. The results of this study show different effects of ionizing radiation on two adaptive enzymes, both in chickens and rats. Gamma radiation, rat, chick, alanine aminotransferase, aspartate aminotransferase There is no doubt that use of nuclear power is one of the important discoveries of the 20th century. However, this discovery poses risks to humans and other living systems, whether in the form of nuclear weapons, increasing radioactive background, or accidents with technical equipment intended for peaceful use of nuclear energy. This indicates a need for continuous study of harmful effects of ionising radiation not only on mammals (Flory and Neuhaus 1976; Konecna and Kal ina 1987; Maruyama and Feola 1987; Kal ina et al.1994; stanikova et al. 1994; Cigankova et al. 1996) but also on other species (sesztakova 1996; Skardova et al. 1994). at the same time, new radioprotective substances are searched for and tested with the aim to decrease the radiation damage (Fedorocko et al. 1992, 1994). adaptation of organisms to changes in the external environment is achieved through a sequence of very closely related adaptive processes which result eventually in a new balance between an organism and its environment. With respect to this it is important that individual changes do not necessarily result from the original stimulus but they constitute most frequently a response to the changes in the preceding link of the adaptive chain. adaptation may be induced by prolonged continuous or intermittent stimuli. They may include, besides cell plasma-nucleus relations, also such regulatory mechanisms that ACTA VET. BRNO 2003, 72: 201–205 Address for correspondence: MvDr. Katarina Beňova, phD. Department of radiobiology University of veterinary Medicine Komenskeho 73, 041 81 Kosice, slovak republic phone: +421 55 633 8175 Fax: +421 55 63 23 666 e-mail: benova@uvm.sk http://www.vfu.cz/acta-vet/actavet.htm