The effect of iodine and strumigens long-term foodborne intake on histometrical parameters of thyroid gland in gimmers

PEKSA ZDENĚK, TRAVNICEK JAN, KONECNÝ ROMAN, JELINEK FRANTISEK, DUSOVA HANA, VOLFOVA KATEŘINA, VRBOVA ANETA, ZABRANSKÝ LUBOS, FALTA DANIEL, PALKA VACLAV: The eff ect of iodine and strumigens long-term foodborne intake on histometrical parameters of thyroid gland in gimmers. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 5, pp. 1365–1369 In 2010 and 2011 two experiments on gimmers of Sumava mountain sheep were performed. The fi rst experiment was carried out on 12 animals (experimental period was 11 months); control group was fed with 3 mg I*kg−1 in dry matter per day and experimental group was fed with 5 mg I*kg−1 in dry matter per day. The second experiment lasted 10 months and it was carried out on 12 animals. Feed ration for control group contained 10 mg I*kg DM−1. Feed ration for experimental group contained 10 mg I*kg DM−1 too; moreover it included rapeseed meal and 1 g of sodium nitrate. The aim of the fi rst experiment was focused on impact of high iodine intake on structure of thyroid gland. The aim of the second experiment was to discover eff ect of strumigens during high iodine intake on structure of thyroid gland. The animals were slaughtered a er the experiment and there was executed the dissection of thyroid gland. The samples of thyroid gland were processed during classic paraffi n method and dyed with haematoxylin and eosin. For fi nding of histometrical parameters was used program Leica IM 500 Version 4.0. The length, the width and the area of follicles were measured. The follicles were divided into three groups a er this procedure (by the length); in each group were measured 20 thyreocytes. In group with intake 5 mg I*kg DM−1 (experiment from year 2010): higher weight of thyroid (p < 0.01), signifi cant higher (p < 0.05) proportional representation of large and medium follicles, signifi cantly (p < 0.05) higher average size of follicles, demonstrably lower (p < 0.05) height of epithelium were found. There were not found any diff erences in monitored parameters between the groups from experiment which was carried out during the year 2011. A er comparing results from the both experiments signifi cantly higher percentage representation of large follicles a signifi cantly lower representation of small follicles, distinctly higher average size and higher height of epithelium in all size categories, in groups with iodine intake 10 mg I*kg DM−1was found (from second experiment – year 2011). follicle, epithelium, thyreocyte, rapeseed meal, nitrates, morphometry Thyroidal hormones crucial aff ect the whole metabolism of organism. Iodine intake from the environment is the critical factor, which infl uences function of thyroid gland. The thyroid gland in sheep is in region of the fi rst tracheal ring, thyroid is formed from two lobes, which are connected by istmus. Normal thyroid weight is approximately 3–7 grams in adult sheep (Kratochvil, 1998). The longterm insuffi cient or superfl uous iodine intake may be refl ected on function and structure of thyroid 1366 Z. Peksa, J. Travnicek, R. Konecný, F. Jelinek, H. Dusova, K. Volfova, A. Vrbova, L. Zabranský, D. Falta, V. Palka gland. The long-term lack of iodine caused: decrease of production thyroidal hormones -thyroxine and triiodothyronine, growing of epithelial cells, reduction of follicles size and growing of gland weight (Kratochvil, 1998). The long-term high iodine intake caused hyper function of thyroid gland at the young age (later to hypo function, due to reduced production of TSH – thyroid stimulating hormone). There was found relationship with development of autoimmune disease of thyroid gland in human (Burgi, 2010; Guan et al., 2009; Dal Maso et al., 2009; Knobel and Medeiros-Neto, 2007). Thyroidal hormones infl uence production (milk yield, intensity of growth, growth wool) and reproduction of animals (Pugh and Baird, 2012). The impact of iodine excess on thyroid structure may be refl ected in reduce of height of thyreocytes, an increase of follicles size due to accumulation of colloid. The weight of thyroid is usually lower, in some cases the weight of thyroid gland grows due to accumulation of colloid (colloid goitre) (Deborah and Stabenfeldt, 2007; Zachary and McGavin, 2011). The aim of this work was focused on infl uence of long term foodborne high intake of iodine and strumigens on structure and others parameters of thyroid gland. MATERIAL AND METHODS In 2010 and 2011 two experiments on barren gimmers of Sumava mountain sheep bread were performed. Animals from both experiments were come from the same breed and were bred in the same conditions. The both experiment group were fed with experimental feeding mixture and ad libitum hay. Animals were (12 barren gimmers) burdened with high iodine foodborne intake during 11 months in year 2010. The control group (group A) received 3 mg I*kg DM−1 and experimental group (group B) received 5 mg I*kg DM−1. Average body weight was 74–88 kg and average age was 24 months. The second experiment (in year 2011) was carried out on 12 animals and experimental time was 10 months. The control group (group C) received feeding mixture 10 mg I*kg DM−1, the experimental group (group D) was fed with mixture with the same iodine concentration, moreover the experimental feeding mixture rape seed meal and sodium nitrate (1g per head and day). The aim of this experiment was focused on the impact of strumigens (glukosinolates and sodium nitrate) on structure of thyroid gland by high iodine intake. The animals were slaughtered in slaughterhouse a er experiment, the thyroid glands were dissected, weighted and samples for histological examination were fi xed in 10% neutral buff ered formalin, embedded in paraffi n wax, sectioned at 5 μm thick slices and stained with haematoxylin and eosin. Histometrical measurement was carried in program for image analysis Leica IM 500 Version 4.0. , (in combination with camera Leica DC 320 and microscope Leica DM 2500). The length, the width and the area of 60 follicles were measured in three visual fi elds (from diff erent parts of slice). Measured follicles were divided into three categories (Jelinek et al., 2003): large (175.1–615.0 μm), medium (80.1– 175.0 μm), small (15.0–80.0 μm). The proportion of these categories was found. Dates were processed in program STATISTICA 7.0. (StatSo , Inc.), Anova and regression and correlation analysis were used.