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Сельскохозяйственная биология, 2010, № 6, с. 104-107.

УДК 636.2:619:574.24:591.11

NATURAL RESISTANCE AND PATHOLOGY OF THYROID IN CATTLE AFTER CHERNOBYL’ ACCIDENT

V.Ya. Sarukhanov, N.N. Isamov

Histological structure of the thyroid, hormonal status and humoral resistance factors (bactericidal and β-lytic blood properties) in animals with hypotheriosis caused by incorporated ¹³¹I has been studied. It has been found that at an absorbed dose to the organ of 356 Gy, parenchyma is replaced by connective tissue, which reduces the level of thyroid hormones in the blood by 80% compared to the control. Animal hypotheriosis results in decrease in β-lytic and bactericidal activity of blood to Salmonella enteritidis. The irradiation of the thyroid at a dose of 30 Gy does not induce its marked changes.

Key words: cattle, thyroid gland, hormones, natural resistance, irradiation, ¹³¹I.

 

Biological effects of incorporated radionuclides are determined by their physicochemical properties and contents in a critical organ. Thus, accumulation of ¹³¹I in the thyroid gland may cause its complete destruction and resulting hypothyroidism, worsening of general condition, reduced productivity and resistance of animals (1). Natural resistance largely depends on bacteriolysines that affect mainly gram-positive (complement system) and gram-negative microflora. (β-lysines, lysozyme). The complement system is currently studied in detail, while the number of works focused on β-lysines is quite small. High levels of β-lytic activity of the blood indicate the raise of compensative and adaptive processes in the body at various physiological and pathological conditions, while the reduce of these levels accompanies pathological processes of medium and heavy severity (2). In model experiments on laboratorial and farm animals, radiation sickness was accompanied by inhibition of bactericidal activity in the blood at medium severity disease,  and by reduce in β-lytic activity – at a severe disease (3, 4).

Irradiation of the thyroid gland reduces natural resistance of animals. For example, the introduction to chickens of 1573 kBq ¹³¹I increased microbial colonization in the pharynx in more than 60 times compared with control (5). White rats subjected to 150-290 Gy per the thyroid gland demonstrated phase changes in bactericidal and lysozyme activity of the blood (6).

The territory of Belarus Polesie relates to the geochemical province with a deficit of stable iodine, which could contribute to the increased accumulation of ¹³¹I in the thyroid gland during first weeks after the Chernobyl accident (7). This has led to hypothyroidism in animals, and, probably, affected the factors of natural resistance of the organism (8).

The purpose of this study was to examine humoral factors of natural resistance and histological structure of the thyroid gland in animals affected by radiation exposure during the Chernobyl accident.

Technique. The study was carried out on cows the Black-and-White breed in 1986-1987 (60 goal). The animals of group I were evacuated to vivarium of the All-Russia Research and Development Institute of Agricultural Radiology and Agroecology (Obninsk) from the Vetkovskii region (Gomel province of Belarus) (dose - 30 Gy to the thyroid gland). Group II were the cows of the farm “Pervomaysky” (Braginskii region, Gomel province) (Dose - 356 Gy). The control - group III - were intact animals (Meschovsky region, Kaluga province).

Blood samples were obtained from the jugular vein in the morning before feeding animals. The plasma was separated by centrifugation at 3000 rpm for 15 min. Thyroid hormones were determined using the kits Amerlex-MFree T4 RIAkit and Amerlex-MFree T3 RIAkit (“Amersham”, UK). Bactericidal activity of the blood (BAC) was measured according to the modified technique of O.V. Bukharin and N.V.Vasil’ev (7), the activity of  β-lysine (BLA) – by photonephelometry (3). (7), Titer of normal antibodies was determined by generally accepted method (9). Histological studies of the thyroid gland were performed on prepared paraffined sections after staining with hematoxylin and eosin (10).

Statistical processing of data was performed with calculation of mean and the average error in Microsoft Excel.

Results. Histological examination of the thyroid gland in the control group of animals revealed no pathological changes. group I demonstrated slight hardening of the gland; in group II, parenchyma of the thyroid gland was replaced by dense connective tissue strands (10).

In 7 months after the accident, Group I demonstrated the reduce in contents of total thyroxine and triiodothyronine by 70%, free thyroxine was higher than in control and triiodothyronine - 50% lower. After 8 and 9 months, these indices reversed to normal values (Table 1). In group II, contents of total thyroxine and triiodothyronine was lower than control, respectively at 80 and 90%, free thyroxine and triiodothyronine – respectively, 30 and 60% (Table 1).

In group I, bactericidal activity of blood against Escherichia coli and Salmonella in 7 months after the accident amounted to 64,6 ± 0,90 and 55,9 ± 0,80%, i.e., below the physiological norm (70 and 65%) . Later, this parameter returned to normal level. During all time of the study, β-lytic activity exceeded the norm (35,0 ± 12,50%) and reached 50% in some animals. In addition, these cows demonstrated twice increased antibody titer. In group II, bactericidal activity of blood was also below the physiological norm, and amounted to 54,6 ± 3,70% - for salmonella, 66,4 ± 3,50% - for E. coli. The activity of  β-lysine was at the lower limit of the physiological norm (20,5 ± 2,50%), and didn’t exceed 17,5% in some animals (Table 2).

Thus, doses of absorbed radiation determined the extent of damage to the thyroid gland and contents of hormones in the blood of animals. For example, after the dose of 356 Gy , the parenchyma of thyroid gland was replaced by connective tissue which reduced the content of thyroid hormones in the blood. This process was accompanied by reduce in β-lytic and bactericidal activity of blood against Salmonella. The slight decrease of thyroid hormones’ content in blood plasma after the radiation exposure of 30 Gy per thyroid can be connected with the deficit of stable iodine in a diet, since the territory of Gomel region is the endemic biogeochemical province.

The authors thank N.A. Vasil’eva for performing histological studies of the thyroid gland.

REFERENCES

1. Budarkov V.A., Chronic Radiation Disease in Ruminants and Chickens at Internal Irradiation with Radioactive Iodine, in Mat. Vseros. nauch. konf. “Nauchnye osnovy vedeniya agropromyshlennogo proizvodstva v usloviyakh krupnykh radiatsionnykh avarii” (Proc. All-Russia Sci. Conf. “Science Basics of Agricultural Management after Serious Radiation Incidents”), Obninsk, 1998, p. 136.
2. Bukharin O.V. and Vasil’ev N.V., Sistema beta-lizina i ee rol’ v klinicheskoi i eksperimental’noi meditsine (System of Beta-Lysine and Its Role in Clinical and Experimental Medicine), Tomsk, 1977.
3. Sarukhanov V.Ya. and Isamov N.N., Beta-Lytic Properties of Blood in Agricultural Animals after Action of Ionizing Radiation, S.-kh. biol., 2005, no. 2, pp. 116-118.
4. Sarukhanov V.Ya. and Isamov N.N., Bactericidal Properties of the Blood in Different Species of Agricultural Animals under the Influence of Starvation and Irradiation, S.-kh. biol., 2001, no. 2, pp. 80-83.
5. Baklanova V.S., The Influence of 131I on Bactericidal Properties of Pharynx in Chickens, in Mat. 3-j nauch.-prakt. konf. “Ispol’zovanie radioizotopov i ionizirujuschikh izluchenii v veterinarii i zhivotnovodstve” (Proc. III Sci.-Pract. Conf. “The Use of Radioactive Isotopes and Ionizing Radiation in Veterinary and Animal Husbandry), Moscow, 1973, p. 17.
6. Nevstrueva M.A., Shubik V.M. and Tokin I.B., Vliyanie inkorporirovannykh radioizotopov na immunologicheskie protsessy (The Influence of Incorporated Radioisotopes on Immunity Processes), Moscow,  1972.
7. Koval’skii V.V., Geokhimicheskaya ekologiya: Ocherki (Geochemical Ecology: Essays), Moscow, 1974.
8. Isamov N.N., Koz’min G.V., Kruglikov B.P. et al., State of Health of Agricultural Animals on the Territories Affected by the Radioactive Contamination Resulting the Chernobyl Nuclear Power Plant Accident, Radiatsiya i risk, 1997, no. 9, pp. 71-75.
9. Bolotnikov I.A., Immunoprofilaktika boleznei ptits (Immunoprophylaxis of Diseases in Birds), Moscow, 1982.
10. Androsov F.Z., Belyaev I.Ya., Klochko R.T. et al., Spravochnik veterinarnogo laboranta (Guidebook for Veterinarian Laborant), Antonov V.Ya., Ed., Moscow, 1981.

 

All-Russia Research and Development Institute of Agricultural Radiology and Agroecology, RAAS,Kaluga province, Obninsk 249020, e-mail: riar@obninsk.org

Received June 6, 2008

All-Russian Institute for Selection and Seed-Breeding of Vegetables All-Russian Selection and Technological Institute of Horticulture and Breeding Nursery Institute of Agricultural Biotechnology Joint Stock Company "GosNIISyntezBelok"