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Zhao Na - "Possible mechanism of the effects of fluoride on the thyroid during embryonic development and lqctation" Guiyang Medical College (2009)
目的:过量摄入氟对机体几乎所有组织均可产生毒性作用,有资料报道:高氟可致甲状腺功能损害,形态损伤,本研究探讨高氟致亲代大鼠甲状腺损害后是否对子代大鼠甲状腺产生损害及探讨可能的损害机制。 方法:将30只Wistar大鼠随机分为正常亲代组(N组)10只、高氟亲代组(F组)20只。正常亲代组饮用自来水,高氟亲代组饮用含NaF 100mg/L高氟水;7个月后经检测证实高氟亲代组大鼠出现甲状腺功能低减后,两组大鼠分别雌雄交配产生子代大鼠(分别为n、f组);哺乳期间母鼠继续饮用高氟水,30天后分笼;两组子代大鼠均以自来水加正常饲料饲养,4个月后取材。放免法测定血清TT3,TT4;HE染色观察甲状腺形态结构;免疫组化方法检测甲状腺组织谷氨酸受体NR2B亚单位表达的改变。 结果:(1)血清TT3,TT4改变:高氟子代组(f组)TT3明显低于正常子代组(n组)(P0.05),TT4亦有降低趋势。(2)HE染色显微镜观察甲状腺形态结构改变:n组大鼠甲状腺滤泡上皮结构正常,排列有序,滤胞无增生或萎缩。f组均表现滤泡上皮增生,数量及层次增加,排列紊乱,细胞呈柱状或高柱状,甚至可向滤泡腔突出形成乳头;部分滤泡内胶质减少,滤泡腔空虚,红染均质胶状物减少;部分甲状腺组织坏死,结构破坏,细胞结构不清,核消失;部分间质血管扩张充血,管腔增大,充满;部分间质有炎细胞散在浸润;部分间质纤维组织呈灶性或弥漫性增生。(3)甲状腺组织内NMDA受体亚单位NR2B免疫组化染色发现,各组甲状腺均有NR2B受体的表达,NR2B受体免疫组化染色呈棕黄色,主要着色在甲状腺腺泡上皮细胞的胞膜及胞浆。测量各组平均光密度:正常亲、子代组分别为122.99±4.17,115.17±6.46,两组无差异性;高氟亲代组为169.32±15.21,高氟子代组为94.00±13.33;F组NR2B阳性细胞较N组显著减少,f组NR2B阳性细胞较n组显著增多,各组之间平均光密度均值FN/nf(P均0.01)。 结论: 1.亲代大鼠过度染氟可导致子代大鼠甲状腺功能低减、形态结构损伤。 2.子代大鼠出生后即使较长时间脱离高氟环境,甲状腺功能低减、形态结构损伤仍难以逆转。 3.上述结论提示在氟中毒病区,关注孕妇、胎儿和新生儿甲状腺功能都十分重要;脱离高氟环境的胎儿和新生儿的甲状腺功能也要引起我们的关注。由于以替代治疗纠正甲状腺功能低减是简便、易行、有效和相对安全的,故一旦发现甲状腺功能低减应及时以TH或甲状腺制剂进行替代治疗。 4.免疫组化染色发现大鼠甲状腺有NR2B受体表达。 5.亲代大鼠过度染氟可导致亲子两代甲状腺NR2B受体表达异常,这可能是谷氨酸兴奋性毒性的表现。 6.NR2B受体导致甲状腺损伤的机制可能构成氟中毒致组织损伤的重要机理。
Objective
Excessive intake of fluoride can exert toxic effects on nearly all tissues of the body. Reports indicate that high fluoride exposure can cause thyroid dysfunction and morphological damage. This study explored whether parental exposure to high fluoride, resulting in thyroid damage, would also cause thyroid damage in offspring, and investigated the possible mechanisms of such injury.
Methods
Thirty Wistar rats were randomly divided into a normal parental group (N group, n=10) and a high-fluoride parental group (F group, n=20). The normal parental group drank tap water, while the high-fluoride group drank water containing 100 mg/L NaF.
After 7 months, thyroid dysfunction was confirmed in the high-fluoride parental rats. Then, the two groups of rats were bred (producing offspring groups: n and f, respectively). During lactation, mother rats in the F group continued drinking high-fluoride water. After 30 days, the litters were separated, and both groups of offspring were raised with tap water and standard feed. After 4 months, specimens were collected.
Serum TT3 and TT4 were measured by radioimmunoassay.
Thyroid morphology was examined with HE staining.
Immunohistochemistry was used to detect changes in the expression of the NMDA receptor NR2B subunit in thyroid tissue.
Results
Serum TT3 and TT4: TT3 in the high-fluoride offspring group (f group) was significantly lower than in the normal offspring group (n group) (P<0.05). TT4 also showed a decreasing trend.
Morphological changes (HE staining):
n group: thyroid follicular epithelium was normal, orderly arranged, without hyperplasia or atrophy.
f group: follicular epithelial hyperplasia with increased cell number and layering, disordered arrangement; cells were columnar or tall columnar, sometimes protruding into follicular lumen to form papillae. Some follicles had reduced colloid, empty lumina, decreased eosinophilic homogeneous colloid. Some thyroid tissue showed necrosis, structural damage, unclear cellular architecture, nuclear disappearance. Some interstitial blood vessels were dilated and congested, lumina enlarged and filled. Scattered inflammatory cell infiltration was present in some interstitium. Local or diffuse interstitial fibrosis was observed.
Immunohistochemistry (NR2B expression):
NR2B receptors were expressed in thyroid tissue of all groups, with brown-yellow staining mainly located in the membranes and cytoplasm of follicular epithelial cells.
Average optical density: normal parent group 122.99±4.17; normal offspring 115.17±6.46; no difference. High-fluoride parent group 169.32±15.21; high-fluoride offspring group 94.00±13.33.
NR2B-positive cells were significantly reduced in F vs. N group, and significantly increased in f vs. n group (P<0.01).
Conclusion
Excessive fluoride exposure in parental rats leads to thyroid dysfunction and morphological damage in their offspring.
Even after prolonged removal from a high-fluoride environment, thyroid dysfunction and structural damage in offspring are difficult to reverse.
These findings suggest that in fluorosis-endemic areas, monitoring thyroid function of pregnant women, fetuses, and newborns is essential. Even if removed from high-fluoride environments, fetal and neonatal thyroid function requires attention. As replacement therapy for hypothyroidism is simple, effective, and relatively safe, thyroid hormone or thyroid preparations should be administered promptly once dysfunction is detected.
Immunohistochemistry confirmed NR2B receptor expression in rat thyroid tissue.
Excessive parental fluoride exposure caused abnormal NR2B expression in both parent and offspring thyroids, possibly reflecting excitotoxicity from glutamate.
NR2B receptor–mediated thyroid damage may represent an important mechanism of tissue injury caused by fluorosis.