[en] An attempt is made to establish the the time when the prolong impact of slightly increased radiation background get over the compensator mechanisms of living systems. The object of investigation was the ecosystem of the Bay of Wromos (Black Sea, BG) and its surroundings where the flotation slack from an uranium mine was disposed. radioactivity. The following radiobiological picture of the site is obtained according to measurements performed: the alpha-activity of the beach sands is higher than one of the slack and is different in plants; the beta-activity is higher compared to controls in all samples investigated; the gamma spectra show high concentration of the members of U-238 and Th-232 series. The biological effect provoked by this heightened radiation background is studied by means of the isoenzymes as indicators of changes on molecular level. The isoenzyme spectra of lactate dehydrogenase and butyrol dehydrogenase is studied by vertical electrophoresis. The following species are tested: Tettigonia candata charp, Galliptumus italicus, Grillus campestris and Lumbicus terrestrial. An increase in activity and quantity of enzymes as well as changes of their isoenzyme spectra is observed. Calliptumus italicus could be used as a bio indicator of contamination, as it show better separation of the LDH and BDH-isoforms of LDH and BDH, and is more wide-spread. The increase in activity and quantity of some isoenzyme fractions in the conditions of this experiment is one of the possible mechanisms for increase in radioresistance of the living systems. 3 tabs., 2 figs., 8 refs

[en] Changes in isoenzyme spectra of lactate dehydrogenase (LDH) and butyrol dehydrogenase (BDH) in white mice after gamma and neutron irradiation with different doses are studied. After irradiation with 1.75.10^-2 Gy a high intensity in M- and HM-fractions is observed, which is connected with an additional kidney hyper function and hypoxia. After 3.5.10^-2 Gy irradiation the activity and quantity of M-fractions is increased at the expense of H-fractions, which is due to additional burden of liver with intoxications of harmful metabolites. With a dose of 68.32.10^-2 Gy a total increase of activity and quantity of all fractions in the organs investigated is noted, as well as strongly expressed changes in BDH polymorphism. It is concluded that the changes in isoenzyme spectra are connected with a drive to counteraction against the radiation effect and are expressed in an increased enzyme activity. There exists a threshold dose, below which no changes on molecular level can be observed by electrophoretic methods. 7 figs