The reproductive strategy and immune status of rodents in an environment altered by industrial activity

Abstract

27 The nature and mechanisms of animal population adaptation to chronic irradiation is one of the most important problems of modern radioecology. The results of long-term monitoring of mouselike rodent populations in the head portion of the Eastern Ural radioactive trail (EURT) show numerous quantitative and qualitative disturbances in the hemopoietic and immune systems of the animals [1, 2], as well as substantial cytogenetic [3] and morphogenetic [4] alterations. At the same time, the numbers of dominant rodent species in the EURT zone have remained the same as in the background areas for many years, and their fertility is sometimes even higher than the control values [1, 5]. Functions of the immune system are diverse, it is involved in maintenance of the cytogenetic homeostasis, control of offspring quality [6], adaptation [7], and control of ontogeny [8]; immune reactivity is also related to demographic processes. Therefore, it may be presumed that disturbances caused in animals by radioactive contamination of the environment are also related to alteration in the immune system. The results presented below demonstrate that disturbances in the controlling (eliminating) and regulatory functions of the immune system are leading factors of the increase in the reproduction rate of mouselike rodent populations of areas altered by industrial activities and may be regarded as mechanisms of adaptation to radioactive contamination. Experiments were performed to analyze the reproductive characteristics of laboratory mice under the conditions of immunosuppression, and the results of the model experiment were compared with the reproductive parameters of rodents from the EURT and neighboring areas. The immunosuppressant Cyclophosphanum was intraperitoneally injected to females from the experimental group (strain CBA) during seven days before mating; control animals were injected with physiological saline (a total of 84 mice were used). The immunomodulator effect was verified by morphological, physiological, and immunohematological parameters. The fertility parameters and embryo loss were calculated, the total number of the offspring was recorded, and the changes in body weight during early ontogeny were monitored. The Excel software package was used for treatment of the data. The morphological and physiological verification of the immunosuppressant effect showed that the groups significantly differed in almost all indices of internal organs (Table 1). Regarding the hemopoietic system, the experimental group was characterized by a considerable decreased in the cellular density of the bone marrow and spleen, a considerable leukopenia accounted for by a decrease in the main populations of leukocytes