AGRICULTURAL BIOLOGY, 2015, V. 50, ¹ 6, pp. 839-846 ISSN 2412-0324 (English ed. Online) (SEL’SKOKHOZYAISTVENNAYA BIOLOGIYA) ISSN 0131-6397 (Russian ed. Print) ISSN 2313-4836 (Russian ed. Online) Resistance — factors and stimulation doi: 10.15389/agrobiology.2015.6.839rus doi: 10.15389/agrobiology.2015.6.839eng CONTENT OF METALLOTHIONEINS IN THE ORGANS OF SHEEP UNDER CHRONIC INTAKE OF LEAD WITH RATION E.B. MIRZOEV, V.O. KOBYALKO, I.V. POLYAKOVA, O.A. GUBINA, N.A. FROLOVA Federal Agency of Scientific Organizations, 109 km, Kievskoe sh., Obninks, Kaluzhskaya Province, 249032 Russia, e-mail mirzoev.ed@yandex.ru A b s t r a c t When studying the effects of lead on mammals, one of the informative indicators is the level of metallothioneins (MTs) in organs. <...> MTs are low molecular weight proteins (6-7 kDa) containing up to 30 % cysteine which bind heavy metal ions (Cd2+, Zn2+, Pb2+, Hg2+, Cu2+) and act as a trap for free radicals. <...> It is assumed that the MTs content in tissues of mammals depends not only on the amount of lead, the way of intake (with water and/or diet), the type of the tissue and its physiological functions, but on the number of cells in the body and their functional activity. <...> At the same time, the violation in functional and synthetic activity of cells may be related to changes in the weight indices of the bodies. <...> In this regard, the study of MT levels in farm animals as influenced by lead is of interest. <...> In the present work we studied experimentally the MT content, the cellularity and the weight index of the organs in sheep of the Romanov breed under lead intoxication. <...> For 90 days the sheep in groups II (5 animals), III (9 animals) and IV (9 animals) had a daily diet with lead nitrate at 5 mg/kg, 25 mg/kg and 150 mg/kg of feed, respectively, which corresponded to 1, 5 and 30 MPL (maximum permissible levels) of the metal in the feed. <...> The diet consisted of 0.3 kg of concentrate and 2 kg mixed grass hay. <...> Daily intake of metal (on average per animal) was 10 mg in group II, 50 mg in group III, and 300 mg in group IV, and the dose was 0.3, 1.5 and 9 <...>