The Study On The Effects Of Excess Iodine And Excess Tyrosine On Goiter Pathogenesis In Mice

Objective: According to the domestic and foreign the epidemiology investigation and the laboratory research of prevention iodine deficiency disoders (IDD) and the thyroxine synthesis mechanism, Yu Zhiheng proposed the discussion and ponder about etiology of IDD, and that the iodine was the primary cause of IDD , but the function of the tyrosine, the Vitamin and the trace element and so on were also not allowed to neglect. We do some research about the function of tyrosine as one of thyroxine's synthesis raw materials in the prevention IDD(influence of low iodine and low tyrosine on thyroid gland ). But the report has not seen to the influence of high tyrosine and high iodine on thyroid gland.This experiment above the former research foundation plans to further consummate the function of tyrosine to prevent IDD and then lay the foundation for revelation comprehensive of dose effect rule's research of influence of tyrosine on function and morphology of thyroid gland.Methods: 90 healthy mice (weight 12~14g) were divided into 4 groups randomly according to 2×2 factorial experiment design, and every group has 11 male and 11 female mice: (1) Adequate iodine and adequate tyrosine (AIAT), (2) adequate iodine and high tyrosine (AIHT), (3) high iodine and adequate tyrosine (HIAT) and (4) high iodine and high tyrosine (HIHT). 120 days later, a blood sample was taken from medial canthus vein of each mouse, and the content of serum T3, T4, TSH was measured using radio-immunity method after the blood having been centrifuged. Then all animals were decapitated by breaking spinal cord at nuchae. Thyroids were weighted immediately and their relative weights were counted. The pathological changes of the tissue were observed with light microscope and electronic microscope. And the stereological indexes of thyroid such as S, VA, Sf, G and NA were measured using correlated soft. All data was analyzed by SPSS11.0.Results:1. Compared with the AIAT group, in the HIAT group, the thyroid volume increased; the weight and the relative weight increased (P<0.01, P<0.01), and the value of the latter index was increased by 65.49%; the color of thyroid changed into pale from pink; Under light microscope and electronic microscope thyroid formed colloid goiter. Light microscope: follicle and follicle cavity expanded obviously. Follicle epithelial cells changes flat. Colloid obviously increased. Mesenchymal ingredient reduced and blood capillary rarity; electronic microscope: the cell nucleus becomes the flat ellipse. Cell organ reduced. Much of mitochondrion's crista slurred even vanished. Individual mitochondrion swelled. The rough endoplasmic reticulum dilated, and pellet has escaped obviously. The number of the microvilli decreased , small and short. The colloid's electronic density higher; the stereological indexes such as S, VA of the follicle and follicle cavity enlarged while G and NA declined. The changes of the indexes above were significant (P<0.01) except Sf (P>0.05); the content of serum T3 reduced (P<0.05) while T4 elevated (P<0.01). TSH weren't significant (P>0.05). Compared with the AIHT group, the thyroid volume of the HIHT group enlarged markedly, the weight and the relative weight increased (P<0.01, P<0.05), and the value of the latter index was increased by 26.55%; the color changed into pale pink from pink. Light microscope: follicle epithelial cells changes short cubic shape, and follicle cavity expanded. The colloid quantity increased; electronic microscope: the cell nucleus becomes ellipse. Few of mitochondrion's crista slurred . The rough endoplasmic reticulum dilated slightly, and pellet has escaped slightly; the stereological indexes such as S, VA of the follicle and follicle cavity enlarged while G and NA declined. The changes of the indexes above were significant (P<0.05) except Sf ; the content of serum T3,TSH reduced while T4 elevated ,but the changes weren't significant (P>0.05).2. Compared with the AIAT group, in the AIHT group, the thyroid volume reduced slightly; the weight and the relative weight decreased slightly with no significance (P>0.05); the color of thyroid were pink; light microscope: follicle epithelial cells were monolayer cubic shape, and the few proliferated small follicles existed. The colloid distributed even and its color were slightly shallow; electronic microscope: the mitochondrion were rich. The rough endoplasmic reticulum dilated; the stereological indexes such as S, VA and Sf of the follicle and follicle cavity declined while NA and G enlarged but they have no significance (P>0.05); the content of serum T3,TSH elevated while T4 reduced slightly but all weren't significant (P>0.05). Compared with the HIAT group, in the HIHT group, the thyroid volume the thyroid of the HIHT group reduced markedly, the weight and the relative weight decreased (P<0.01, P<0.01), and the value of the latter index was decreased by 27.91%; the color changed into pale pink from pale; light microscope: follicle epithelial cells changes into short cubic shape from platy shape, and follicle cavity reduced. The colloid quantity declined; electronic microscope: the cell organ increased obviously. Mitochondrion were rich and few of their crista slurred. The rough endoplasmic reticulum dilated slightly, and pellet has escaped slightly. The number of the microvilli increased. The colloid's electronic density declined; the stereological indexes such as S, VA of the follicle and follicle cavity declined while G and NA elevated. The changes of the indexes above were significant (P<0.01). The difference of Sf weren't significant (P>0.05); the content of serum T3 elevated (P<0.05) while T4 reduced (P<0.01). TSH elevated with no significance (P>0.05).3. Iodine and tyrosine had interactive effects on the indexes such as thyroid weight, relative weight, T3, T4 and stereology except body weight, TSH and Sf . 4. From the AIAT group to the AIHT group to the HIHT group to the HIAT group goiter rate increased in turn. They respectively are 0%, 0%, 35%, 89.5%. Model difference was significant (P<0.01). Goiter rate of the HIAT group was much higher than that of the AIAT group (P<0.01); HIHT group was still higher than AIHT group (P<0.01); compared with the AIAT group, in the AIHT group, the difference of goiter rate wasn't significant (P>0.05); HIHT group was lower than HIAT group (P<0.01). Iodine and tyrosine had interactive effects on the changes of the goiter rate.Conclusions:1. Excess iodine could result in colloid goiter in mice when tyrosine was at adequate or high level. The goiter degree reduced obviously when tyrosine was at high level .2. When iodine was adequate, excess tyrosine has no significant effects on mice; but when iodine was high level , it could reduce harm of excess iodine to thyroid gland obviously.3. Excess Iodine and excess tyrosine had obvious interactive effects----- antagonistic effects on the happen and development of goiter.4. According to the results of this study, excess tyrosine have the protective function to colloid goiter caused by excess iodine.