畜牧兽医学报  2022, Vol. 53 Issue (1): 122-131. DOI: 10.11843/j.issn.0366-6964.2022.01.012    PDF    
灌胃左旋甲状腺素(L-T4)对妊娠小鼠胎盘中DIO3基因表达及胚胎数的影响
赵娟, 李立煊, 陈雯敏, 肖金龙, 仲涛     
四川农业大学 畜禽遗传资源发掘与创新利用四川省重点实验室,成都 611130
摘要:旨在探究小鼠胚胎发育过程中DIO3的表达模式和灌胃左旋甲状腺素(L-T4)对孕鼠胎盘中DIO3基因表达和胚胎数的影响,以期为研究妊娠期母体甲状腺激素异常提供基础数据。本研究以6周龄健康昆明小鼠(雌鼠70只,雄鼠35只)为试验对象。雌鼠经适应性饲养1周后,腹腔灌胃10 U PMSG(溶于0.3 mL生理盐水),正常饲喂48 h后将雄鼠和雌鼠以1∶2的比例合笼过夜。次日清晨对雌鼠进行阴道检测,若阴道处可见乳白色阴栓则视为妊娠第1天。将妊娠小鼠随机分为5组,试验组小鼠分别灌胃0.25(SG, n=10)、1.25(MG, n=10)、2.50(LG, n=10) 和5.00 μg·μL-1(HG, n=10)的L-T4,对照组小鼠给予等量生理盐水(CG, n=10),每天灌胃80 μL,持续10 d。采集试验组妊娠天数分别为第10和18天的小鼠胎盘(n=4/组)并记录胚胎数。此外,采集对照组第10、14和18天的胎盘及未妊娠小鼠卵巢(n=3/组)。利用RT-qPCR、原位杂交和免疫组化技术检测小鼠胎盘组织中DIO3的表达情况,利用化学发光仪检测妊娠小鼠灌胃L-T4后血清中TSH、FT3和FT4的含量变化。RT-qPCR结果表明,在正常生理条件下,胎盘组织中DIO3的表达水平随妊娠时间增长呈递减趋势,在妊娠期第10天时表达量最高,在第18天时表达量最低,且低于未妊娠时的表达量(P<0.01)。石蜡切片显色原位杂交及免疫组化分析与RT-qPCR结果一致。灌胃L-T4后,母鼠体内血清TSH、FT3和FT4水平均随灌胃浓度的增加呈现升高趋势,且各处理组间差异显著(P<0.05)。此外,DIO3的表达随灌胃剂量的增加而增加。妊娠第10天,DIO3的表达量在对照组与HG组之间呈极显著差异(P<0.01),对照组与SG组、MG组和LG组之间无显著差异。妊娠第18天,对照组DIO3的表达量显著高于灌胃组(P<0.01)。妊娠第10天灌胃组妊娠母鼠胚胎数量略大于对照组,但差异不显著;妊娠第18天灌胃组和对照组妊娠母鼠胚胎数量大致相同。综上所述,灌胃L-T4可提高妊娠母鼠血清中甲状腺激素水平,诱导胎盘组织中DIO3的表达。但灌胃L-T4对妊娠母鼠的胚胎数无显著影响。本研究结果为进一步研究妊娠期甲状腺激素水平调控的分子机制提供了理论基础。
关键词小鼠    妊娠期    DIO3    基因表达    甲状腺激素    
Effects of Levothyroxine (L-T4) by Gavage on DIO3 Expression in Mice Placenta and Embryo Number
ZHAO Juan, LI Lixuan, CHEN Wenmin, XIAO Jinlong, ZHONG Tao     
Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
Abstract: The aim of this study was to investigate the expression pattern of DIO3 during the embryonic development in mice, assess the effects of intragastric gavage of levothyroxine (L-T4) on DIO3 expression and embryo number, and provide basic data for the study of maternal thyroid hormone abnormalities during pregnancy. In this study, the healthy Kunming mice (70 females, 35 males) aged 6 weeks were used as experimental objects. After adaptive feeding for one week, female mice were given intraperitoneal intragastric administration of 10 U PMSG (dissolved in 0.3 mL normal saline). After normal feeding for 48 h, male and female mice were caged together at the ratio of 1∶2 overnight. Once the milky vaginal suppository was visible in the morning of the next day, it was considered as the first day of pregnancy. Pregnant mice were randomly divided into 5 groups. The mice in experimental groups were intragastric administrated with 0.25(SG, n=10), 1.25(MG, n=10), 2.50(LG, n=10) and 5.00 μg·μL-1(HG, n=10) of L-T4, re-spectively, and the control group was intragastric administrated with the same amount of normal saline(CG, n=10), 80 μL per day for 10 days. Placentas were collected from mice in exprmental groups on the 10th and 18th day of gestation (n=4/group) and the numbers of embryos were recorded. In addition, ovaries of non-pregnant mice and placentas of mice from the control group on the 10th, 14th and 18th day of gestation (n=3/group) were collected. The expression of DIO3 in placentas of mice was detected by RT-qPCR, in situ hybridization and immunohistochemistry. The contents of TSH, FT3 and FT4 in serum of pregnant mice were detected by chemiluminescence meter after intragastric administration of L-T4. The results of RT-qPCR showed that, under normal physiological condition, the expression level of DIO3 in placenta decreased with the increase of gestation time, and the highest expression level was found on the 10th day of gestation, and the lowest expression level was found on the 18th day of gestation, which was lower than that in non-gestation (P < 0.01). In situ hybridization and immunohistochemistry analysis of paraffin sections were consistent with the results of RT-qPCR. The serum levels of TSH, FT3 and FT4 increased with the increase of concentration of L-T4 intragastric administration, and the differences among groups were significant (P < 0.05). In addition, the expression of DIO3 increased with the increase of intragastrically administered dosage of L-T4. On the 10th day of gestation, there was a significant difference in DIO3 expression between the control group and HG group (P < 0.01), there was no significant difference between the control group and the SG, MG and LG groups. On the 18th day of gestation, the expression of DIO3 in the control group was significantly higher than that in gavage groups (P < 0.01). On the 10th day of gestation, the number of embryos of pregnant mice in the gavage groups was slightly higher than that in the control group. On the 18th day of gestation, the number of embryos of pregnant female mice in the control group and the gavage groups was approximately the same. In conclusion, intragastric administration of L-T4 could increase the level of thyroid hormone in the serum of pregnant mice and induce the expression of DIO3 in the placenta. However, intragastric administration of L-T4 had no significant effect on the number of embryos in pregnant mice. This study provides a theoretical basis for further study on the molecular mechanism of thyroid hormones level regulation during pregnancy.
Key words: mice    gestation    DIO3    gene expression    thyroid hormones    

甲状腺激素(TH)对动物机体维持正常生长发育和新陈代谢至关重要,主要参与调控骨骼、脑和生殖器官的生长发育,且会影响神经细胞增殖、分化和迁移[1-3]。正常生理状态下,在中枢神经系统的调控下,下丘脑释放促甲状腺激素释放激素(TRH)调节腺垂体促甲状腺激素(TSH)的分泌,后者则刺激甲状腺细胞分泌TH。妊娠期间,母体的“下丘脑-垂体-甲状腺轴”存在特殊应激反应,下丘脑中的TH/TH受体(TRs)可通过TH/TRs-亲吻促动素(kisspeptin,KISS)-促性腺激素释放激素(GnRH)通路、TH/TRs-GnRH通路以及室管膜细胞可塑性的改变共同调控GnRH神经脉冲的释放,由雌激素和人绒毛膜促性腺激素(HCG)影响甲状腺的功能,通过负反馈作用调节甲状腺激素的分泌[4-5]。近年来,妊娠期甲状腺激素异常已成为临床常见病。妊娠期甲状腺激素异常不仅会对母体的健康产生影响,还会影响胎儿神经系统、骨骼、大脑和生殖器官的发育[6]。甲状腺激素主要有两种:T4(甲状腺素)的分泌量大,被认为是促激素;T3(三碘甲状腺原氨酸)的分泌量较低,但生物活性高。这两种激素与血清蛋白结合后,由不同类型的细胞膜转运蛋白转运到靶细胞中。进入靶细胞后脱碘酶催化T4和T3酚环或酪硅环上碘原子的去除,介导甲状腺激素的活化和失活[7]

目前已知的脱碘酶有3种:Ι型碘甲状腺原氨酸脱碘酶(D1)、Ⅱ型碘甲状腺原氨酸脱碘酶(D2)和Ⅲ型碘甲状腺原氨酸脱碘酶(D3),分别由Ι型硒代脱碘酶基因(DIO1)、Ⅱ型硒代脱碘酶基因(DIO2)和Ⅲ型硒代脱碘酶基因(DIO3)的mRNA编码,它们的催化特性和组织分布各不相同。D1能够与3, 3′, 5-三碘-L-甲状腺氨酸(T3)和3, 3′, 5′-三碘-L-甲状腺氨酸(rT3)进行5-和5′-脱碘反应[8-9];通过外环碘化作用,D2可将激素原T4转化为具有生物活性的激素T3, 并将rT3转化为3, 3′-二碘-L-甲状腺氨酸(3, 3′-T2),从而增加TH的信号传导[10-11];D3是主要的T3和T4失活酶,可通过催化T3、T4分别转化为无生物活性的代谢产物3, 3′-T2和rT3[12-14]。机体内的甲状腺激素水平主要通过脱碘酶的协同作用维持动态平衡,以满足机体需要[15]。在胚胎发育过程中,D3在妊娠子宫、胎盘、胎儿组织中高表达并降解TH,避免胚胎过度或过早暴露于成年甲状腺激素水平[16-17]

DIO3位于delta样同源物1和Ⅲ型碘甲状腺原氨酸脱碘酶(delta-like homologue 1 and type Ⅲ iodothyronine deiodinase,DLK1-DIO3)印记域的最远端,由一个外显子构成,编码Ⅲ型脱碘酶,参与体内甲状腺激素的降解过程。研究表明,敲除DIO3的小鼠视网膜视锥细胞会退化,还可能导致耳聋和耳蜗过早的分化[18-20]。视交叉上核将视网膜接收的不同光照信号传至松果体,通过调控褪黑素的分泌时长调节促甲状腺激素的分泌,进而作用于下丘脑促进DIO3和DIO2的表达。DIO3和DIO2通过调控下丘脑局部T3和T4的动态平衡影响促性腺激素释放激素基因的表达,从而影响季节性发情[21-22]。例如,黑线仓鼠下丘脑DIO3和DIO2在春季和秋季表达量较高,与其繁殖高峰一致,间接证实了DIO3/DIO2可通过调节光周期信号转导间接调控动物的繁殖活动[23-24]。本试验通过分析灌胃甲状腺激素(L-T4)对小鼠胎盘中DIO3的表达及胚胎数的影响,研究妊娠期DIO3与甲状腺激素之间的分子调控机制,为妊娠期甲状腺激素异常的临床治疗提供理论基础。

1 材料与方法 1.1 试验动物

本研究所用6周龄健康昆明小鼠(其中包括70只雌鼠和35只雄鼠),由成都达硕实验动物有限公司提供。

1.2 主要试剂与仪器

甲状腺素(L-T4)购于德国Sigma-Aldrich公司;TRIzol®Reagent购于美国Invitrogen公司;DEPC、DMF购于成都博瑞克生物技术公司;PrimeScriptTM逆转录试剂盒、SYBR® Premix Ex TaqTM II荧光染料试剂盒购于宝生物工程(大连)有限公司。超净工作台(上海隆拓仪器设备有限公司,S.H.S-840U型);实时荧光定量PCR仪(BIO-RAD,CFX96型)。

1.3 试验设计与动物饲养管理

雌性小鼠经适应性饲养1周后,腹腔灌胃10 U PMSG(溶于0.3 mL生理盐水),正常饲喂48 h后将雄鼠和雌鼠以1∶2的比例合笼过夜。次日清晨对雌鼠进行阴道检测,若阴道处可见乳白色阴栓则视为妊娠第1天[25]。将妊娠小鼠随机分为5组,试验组分别灌胃0.25(SG,n=10)、1.25(MG,n=10)、2.50(LG,n=10)和5.00 μg·μL-1(HG,n=10)的左旋甲状腺素,对照组给予等量的生理盐水(CG,n=10),每天灌胃80 μL,持续10 d。观察母鼠怀孕情况并记录妊娠天数,采集试验组妊娠天数分别为第10和18天的小鼠胎盘(n=4/组)并记录胚胎数。此外,采集对照组第10、14和18天的胎盘及未妊娠小鼠卵巢(n=3/组)。

动物房温度为(20 ± 2)℃,相对湿度为40%~70%,自然光照下,每3天对鼠笼清洗消毒并更换垫料。试验期间小鼠可自由采食和饮水。

1.4 小鼠胎盘组织石蜡切片显色原位杂交检测

小鼠经折颈法处死[26],采集妊娠第10、14和18天小鼠胎盘组织用石蜡包埋后制片,每个时期取1只小鼠。剩余的胎盘组织经液氮速冻后置于-80 ℃冰箱中冷冻保存。将切片依次浸入二甲苯、分级乙醇中,随后用DEPC水清洗。用蛋白酶K(3%柠檬酸稀释)37 ℃消化25 min,PBS液冲洗。预杂交后,滴加含有探针DIO3 mRNA(BIO-5′-GGTCTGGGCGCAGAGCCTCAGCGAGTGAAG-CAG-3′)的浓度为5 ng·μL-1的杂交液,37 ℃杂交过夜。将切片在37 ℃下洗涤15 min,室温洗涤10 min。滴加封闭血清BSA和亲合素化过氧化物酶,然后用DAB和苏木素显色,脱水后封片。将其置于显微镜下镜检,采集图像并分析。

1.5 小鼠胎盘组织石蜡切片免疫组化分析

采集各妊娠期小鼠胎盘组织制成石蜡切片,每个时期取1只小鼠。脱蜡后放入EDTA(pH 9.0)缓冲液中抗原修复。冷却后放入PBS(pH 7.4)中脱色。将玻片放入3%过氧化氢溶液中,室温下避光25 min,PBS冲洗15 min。加3% BSA或10%兔血清,室温封闭30 min。甩掉封闭液,一抗4 ℃下孵育过夜;用PBS冲洗15 min,二抗室温下孵育50 min。PBS冲洗15 min,滴加DAB显色液,水洗终止显色。用苏木素染液轻度复染3 min后水洗,树脂封片,采集镜检图像并分析。

1.6 小鼠血清中甲状腺激素水平检测

对小鼠进行眼眶取血,采集的血样送到四川省八一康复医院,用CHEMCLIN®600全自动化学发光仪测定妊娠第10天小鼠血清中FT3、FT4和TSH水平。

1.7 胎盘组织RNA的提取与反转录

采用TRIzol法提取胎盘组织样中的总RNA[27]:将提前冻存的组织样在液氮中迅速研磨成粉,称取100 mg组织放入1 mL TRIzol中,按试剂盒说明书提取RNA,-80 ℃保存备用。使用琼脂糖凝胶电泳和核酸蛋白仪检测RNA的质量和浓度。使用反转录试剂盒PrimeScriptTM将RNA反转录成cDNA,过程按照说明书进行,cDNA保存于-20 ℃备用。

1.8 DIO3引物设计与合成

以GenBank中小鼠DIO3 mRNA序列(NM_172119.2)为模板,利用Primer Premier 5.0软件设计引物。F: 5′-CCTGAGCCCGAAGTAGAG-3′,R: 5′-GGTCCCTTGTGCGTAGTC-3′,预期产物大小237 bp,退火温度61.4 ℃。以GAPDH为内参基因,F: 5′-GGTGAAGGTCGGTGTGAACG-3′,R: 5′-CTCGCTCCTGGAAGATGGTG-3′,预期片段大小233 bp,退火温度59.5 ℃。引物由成都擎科梓熙生物技术有限公司合成。

1.9 荧光定量PCR检测基因表达

PCR反应体系为10 μL:SYBR® Premix Ex TaqTM II 5 μL,上、下游引物各0.5 μL,cDNA模板0.8 μL,RNase-free ddH2O 3.2 μL。PCR扩增反应的程序为:95 ℃预变性30 s;95 ℃变性10 s,60 ℃退火30 s,72 ℃反应10 s,30个循环;72 ℃延伸5 min。

1.10 数据分析

采用相对定量分析方法,以GAPDH作为内参基因,利用2-ΔΔCt法分析DIO3的相对表达量。利用GraphPad Prism 5.0统计软件进行分析和制图,数据用“平均数±标准误”表示。P<0.05代表差异显著,P<0.01代表差异极显著。

2 结果 2.1 DIO3基因在妊娠小鼠胎盘组织中的表达

利用RT-qPCR技术检测妊娠期第10、14、18天的小鼠胎盘组织以及未妊娠母鼠卵巢组织中DIO3基因的mRNA表达情况。结果显示,DIO3的表达水平随妊娠时间增长呈递减趋势,其中第10天表达量最高;之后降低,在第18天表达量最低,且低于未妊娠时的表达量。DIO3在4个妊娠时期的表达呈极显著差异(P<0.01,图 1)。

数据柱形标注不同大写字母表示差异极显著(P<0.01),下同 The different capital letters above the bars show very significant differences(P < 0.01), the same as below 图 1 DIO3基因在不同妊娠期小鼠胎盘组织中的表达量 Fig. 1 DIO3 gene mRNA expression in placenta of mice at different gestation stages
2.2 石蜡切片显色原位杂交及免疫组化分析

为进一步检测妊娠小鼠胎盘组织中DIO3基因的表达情况,利用石蜡切片显色原位杂交技术对不同妊娠时期的小鼠胎盘组织内DIO3基因mRNA进行亚细胞定位。原位杂交结果显示,DIO3在不同妊娠时期均有表达,其中在妊娠第10天的小鼠胎盘组织中DIO3表达量最高,在第18天的表达量最低,即DIO3基因mRNA的表达量随妊娠发展呈递减趋势(图 2A2B)。利用免疫组化检测不同妊娠时期的小鼠胎盘组织内脱碘酶蛋白含量。免疫组化结果显示,脱碘酶蛋白含量随妊娠发展呈递减趋势,其中第10天的小鼠胎盘组织中最高,在第18天最低,而第14天的蛋白含量介于两者之间(图 2C),与荧光定量PCR和原位杂交结果一致。

A、B. 分别表示不同妊娠期小鼠胎盘内DIO3 mRNA表达量和阴性对照;C表示不同妊娠期小鼠胎盘内DIO3的蛋白水平;细胞核呈蓝色;DIO3 mRNA和蛋白呈棕黄色 A, B. Represent DIO3 mRNA expression and negative controls in mice placentas at different gestation periods, respectively; C. Represents the protein level of DIO3 in mice placentas at different gestation periods. The nucleus is blue; DIO3 mRNA and protein are brownish yellow 图 2 不同妊娠期小鼠胎盘组织中DIO3原位杂交(A、B,200×)及免疫组化(C,400×)结果 Fig. 2 In situ hybridization(A, B, 200×)and immunohistochemical(C, 400×)results of DIO3 in mice placentas at different gestation periods
2.3 灌胃L-T4对孕鼠血清TSH、FT3、FT4水平及胚胎数的影响

利用灌胃针将L-T4灌入小鼠胃内,检测发现妊娠母鼠血清中TSH、FT3和FT4的水平变化趋势一致,均随灌胃L-T4浓度的增加呈现升高趋势,且灌胃剂量最高的母鼠血清中甲状腺激素水平最高(图 3A3B3C)。此外,灌胃组母鼠体内的血清TSH、FT3和FT4水平显著高于对照组,且各处理组间差异显著(P < 0.05)。对比分析发现,妊娠第10天灌胃组妊娠母鼠胚胎数量略大于对照组(CG组),但差异不显著;妊娠第18天灌胃组和对照组妊娠母鼠胚胎数量大致相同。除此之外,各灌胃组间妊娠母鼠胚胎数量无显著差异(图 3D3E)。

数据柱形标注不同小写字母表示差异显著(P<0.05) The different lowercase letters above the bars show significant differences(P < 0.05) 图 3 L-T4对孕鼠血清中甲状腺激素水平及胚胎数的影响 Fig. 3 Effect of L-T4 on serum thyroid hormone level and embryo number in pregnant mice
2.4 灌胃L-T4DIO3表达量的影响

利用RT-qPCR技术检测灌胃不同剂量L-T4的小鼠胎盘组织中DIO3的表达情况。如图 4所示,妊娠第10天时,DIO3的表达随灌胃剂量的增加而增加。DIO3的表达量在对照组与高剂量灌胃组(HG组)之间呈极显著差异(P<0.01),对照组与SG、MG和LG组之间无显著差异(P > 0.05)。妊娠第18天时,对照组DIO3的表达量极显著高于灌胃组(P<0.01)。DIO3的表达随灌胃剂量的增加而增加,但HG与SG组DIO3的表达量无显著差异(P>0.05)。

图 4 不同处理组小鼠体内DIO3基因mRNA表达量 Fig. 4 DIO3 gene mRNA expression level in mice in different treatment groups
3 讨论

DIO3在胎儿组织和新生儿大脑区域中表达,从而有效控制甲状腺激素对胎儿生长发育的影响[28]DIO3可以保护胎儿免受母体高水平T4的侵害,并促进其细胞增殖和生长。本研究结果发现,在正常生理状态下,妊娠时小鼠胎盘中DIO3表达水平显著高于未妊娠时期的水平。另外,小鼠胎盘中DIO3表达量随妊娠发展显著降低,于分娩前达到最低水平,甚至低于未妊娠时期的表达水平。当DIO3缺乏时,会导致胎儿的神经发育异常,表明TH过量的有害作用,并揭示DIO3在调节脑TH行为中的关键作用。在神经元中,DIO3的表达可以使甲状腺激素失活并减少氧气消耗,造成细胞特异性甲状腺功能低下,减少缺血引起的缺氧性脑损伤[29]。TH的状态对性腺的发育和功能有重要影响,在睾丸上表现得尤为明显。TH通过影响睾丸细胞增殖和分化,从而影响睾丸大小、精子生成和类固醇生成[30]

妊娠状态下机体产生的甲状腺激素通过胎盘在胎儿早期的生长发育中发挥关键作用,但胚胎过早暴露于成年甲状腺激素水平可能导致畸形、生长改变、智力迟钝甚至死亡[31]。随着妊娠的发展,胎儿生长变快,妊娠小鼠的代谢随之加快,导致TH的消耗增加,机体局部的TH水平降低,甚至低于未妊娠时期的状态。胎儿和新生儿的血清甲状腺素水平显著低于刚出生几个小时的婴儿[32],这可能是由于胎儿肝以及胎盘DIO3的高表达。DIO3的表达可使甲状腺激素失活,而当TH水平下降时,DIO3的表达量也随之降低,但具体的作用机制还有待查证。出生后TSH快速增加,诱导甲状腺分泌T3和T4及胎盘的缺失,同时DIO1和DIO2表达量增加[33]。大量研究表明,L-T4对治疗轻度甲状腺功能减退症患者有一定效果[34-37]。本试验中,灌胃L-T4的小鼠血清中甲状腺激素水平高于未处理组的激素水平,而且经不同浓度梯度L-T4处理后的妊娠小鼠血清中TSH、FT3、FT4水平随灌胃浓度的增加均呈现升高的趋势,由于这3个指标在临床上能够直观反映甲状腺激素水平,因此,妊娠小鼠体内的TH水平也逐渐升高,表明灌胃L-T4能够促进甲状腺激素的分泌。这与范稣圳等[38]得到的结果相一致。研究表明,鸭蛋清内注射外源性T3会诱导出雏前肝DIO3 mRNA表达降低和出雏后D1和D3蛋白含量及酶活性的降低[39]。本试验中,灌胃L-T4的小鼠DIO3 mRNA表达显著高于未处理组,与上述结果一致。灌胃梯度浓度的L-T4能够诱导甲状腺激素的分泌,同时导致DIO3 mRNA表达量升高,推测可能是甲状腺激素的升高能够促进DIO3 mRNA的表达。

许多研究表明,印记基因DIO3和繁殖性状之间存在某种关联[40-42]。例如,DIO3可通过与DIO2协同作用下丘脑中甲状腺激素的动态平衡,从而影响生殖激素的分泌,调控哺乳动物的繁殖活动[42]。Hernandez等[16]的研究也发现,破坏DIO3的印迹状态或敲除DIO3印记基因会影响D3酶的活性,导致甲状腺激素水平异常,增大死胎率,导致产仔数减少。但在本试验中,妊娠第10天时灌胃组妊娠母鼠胚胎数量略大于对照组,但差异不显著;妊娠第18天灌胃组和对照组妊娠母鼠胚胎数量大致相同。除此之外,各灌胃组间妊娠母鼠胚胎数量无显著差异。这些结果表明,灌胃L-T4可能会诱导胚胎提前形成,但对孕鼠最终胚胎数的影响并不显著,推测DIO3对产仔数的影响可能存在物种差异,仍需进一步研究。

4 结论

综上所述,在正常生理条件下,小鼠胎盘组织中DIO3的表达量随妊娠时间的延长而呈现下降趋势。灌胃L-T4可导致妊娠母鼠血清中甲状腺激素含量增加,进而促进胎盘组织中DIO3的表达。灌胃L-T4对孕鼠最终胚胎数无显著影响。以上研究结果提示,DIO3基因可能与妊娠期小鼠甲状腺激素的动态变化及胚胎发育有关,为进一步研究妊娠期甲状腺激素水平调控的分子机制提供理论基础。

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编辑   郭云雁