王汝平, 王 軍, 孫長(zhǎng)青, 汝少國(guó)

(1.中國(guó)海洋大學(xué) 海洋生命學(xué)院, 山東 青島 266003; 2.中國(guó)海洋大學(xué) 環(huán)境科學(xué)與工程學(xué)院, 山東 青島266003)

有機(jī)磷農(nóng)藥是世界范圍內(nèi)使用最廣、用量最大的高效廣譜殺蟲劑之一[1], 產(chǎn)量占我國(guó)農(nóng)藥總產(chǎn)量的40%以上[2]。農(nóng)藥的使用量中只有不到 1%能對(duì)靶生物起作用, 大部分漂浮在空氣或殘留在土壤中, 并通過降雨、沉降和徑流進(jìn)入河流湖泊造成水體污染。2010年我國(guó)珠江河口流域水體中有機(jī)磷農(nóng)藥檢測(cè)濃度范圍為18.76～344.94 ng/L, 其中甲拌磷已接近人類可接受范圍的臨界點(diǎn)[3]。此外, 邕江、桑溝灣海域、廈門近海等[4-6]多個(gè)水域均檢出有機(jī)磷農(nóng)藥, 可見有機(jī)磷農(nóng)藥對(duì)水環(huán)境質(zhì)量安全和人體健康具有潛在的風(fēng)險(xiǎn)。

近年來的研究表明, 環(huán)境背景濃度的有機(jī)磷農(nóng)藥長(zhǎng)期暴露, 除了能導(dǎo)致大鼠胰腺[7]和硬骨魚類肝胰臟等[8]發(fā)生氧化性損傷外, 還能夠發(fā)揮類雌/抗雄激素效應(yīng), 擾亂睪酮、雌二醇等激素的分泌, 誘發(fā)生殖毒性。例如, 李赟[9]報(bào)道了久效磷暴露誘導(dǎo)雄性孔雀魚(Poeciliareticulata)性腺睪酮水平下降, 雌二醇水平升高; 進(jìn)而導(dǎo)致雄魚交配器長(zhǎng)度和精子數(shù)均顯著降低, 出現(xiàn)第二性征雌性化, 降低了雄魚的繁殖成功率。在馬拉硫磷、二嗪農(nóng)對(duì)硬骨魚類[10-11]及甲基對(duì)硫磷對(duì)大鼠[12]的研究中也有類似報(bào)道。目前有機(jī)磷農(nóng)藥的類雌激素效應(yīng)研究較為深入, 而其抗雄激素效應(yīng)的相關(guān)研究還處于起步階段。本文對(duì)有機(jī)磷農(nóng)藥的類雌/抗雄激素效應(yīng)進(jìn)行了綜述。

1 有機(jī)磷農(nóng)藥的類雌激素效應(yīng)及其機(jī)制

1.1 有機(jī)磷農(nóng)藥類雌激素效應(yīng)

目前在體內(nèi)、體外篩選實(shí)驗(yàn)中, 至少10種有機(jī)磷農(nóng)藥表現(xiàn)出類雌激素效應(yīng)(表1)。有機(jī)磷農(nóng)藥發(fā)揮類雌激素效應(yīng), 能夠誘導(dǎo) 17β-雌二醇(17β-estradiol,E2)、睪酮(testosterone, T)和 11-酮基睪酮(11- ketotestosterone, 11-KT)等性激素水平失衡, 從而導(dǎo)致生殖毒性, 包括改變第二性征、影響生殖器官功能、降低生殖細(xì)胞質(zhì)量等。研究表明, 15 mg/kg樂果使雄性大鼠睪丸內(nèi)T水平下降近50%[21]; 甲拌磷(35, 50 mg/kg)暴露30 d導(dǎo)致雄性大鼠睪丸質(zhì)量減輕, 曲細(xì)精管直徑、睪丸內(nèi)生殖細(xì)胞和支持細(xì)胞數(shù)量均顯著下降[22]。馬拉硫磷能夠顯著抑制雌性黃鱔(Monopterus albus)卵巢芳香化酶活性, 造成 T和 E2水平紊亂[23], 最終導(dǎo)致其卵巢退化[24]。二嗪農(nóng)[25]對(duì)藍(lán)鰓太陽(yáng)魚(Lepomis macrohirus)、久效磷[26]對(duì)斑馬魚(Danio rerio)的影響研究也得到了相似的結(jié)果。同時(shí), 有機(jī)磷農(nóng)藥還能夠?qū)е麓萍に厥荏w(estrogen receptors,ERs)等相關(guān)基因表達(dá)水平的上調(diào)。例如, 樂果暴露能夠誘導(dǎo)雄性大鼠腦、肝臟的ERα、ErβmRNA表達(dá)水平極顯著升高[27]。

具有類雌激素效應(yīng)的有機(jī)磷農(nóng)藥能夠通過擾亂性激素平衡, 導(dǎo)致雄性生殖能力下降; 對(duì)于雌性, 則會(huì)造成床前胚胎丟失率、自然流產(chǎn)率上升, 對(duì)繁殖產(chǎn)生不利影響。Amina 等[28]以樂果(7, 15, 28 mg/(kg·d))染毒雄性小鼠20 d后與雌鼠交配, 結(jié)果顯示雄性交配指數(shù)、生育指數(shù)均顯著降低, 研究認(rèn)為T水平下降以及貯精囊、前列腺等器官損傷是導(dǎo)致雄性性欲降低、生殖力下降的直接原因。同樣, 二嗪農(nóng)能夠降低雄性大西洋鮭(Salmo salar)血漿T含量, 抑制雄魚對(duì)前列腺素 F2α的反應(yīng)性, 從而減弱雄性生殖力[29]。28 mg/kg樂果引起著床所依賴的雌激素、孕激素比例失衡, 進(jìn)而導(dǎo)致小鼠床前胚胎丟失率顯著升高[30]。

表1 發(fā)揮類雌激素效應(yīng)的有機(jī)磷農(nóng)藥

有機(jī)磷農(nóng)藥還能夠通過發(fā)揮類雌激素效應(yīng)影響硬骨魚類的性別分化。魚類的性別決定受多方面的調(diào)控, 主要可分為基因型性別決定和環(huán)境型性別決定[31]。研究表明, 魚類的性別決定主要受發(fā)育的關(guān)鍵窗口時(shí)期胚胎所處的激素環(huán)境影響[32], 因而環(huán)境內(nèi)分泌干擾物自魚類發(fā)育早期開始暴露, 能夠在一定程度上影響其性別分化方向。Zhang等[33]以 0.001,0.010 和0.100 mg/L久效磷農(nóng)藥(40%水溶性制劑)自受精卵起暴露斑馬魚(Danio rerio)至40 dph, 結(jié)果發(fā)現(xiàn)久效磷農(nóng)藥能夠?qū)е掳唏R魚性比偏雌性化,0.100 mg/L暴露組雌性個(gè)體比例高達(dá)71%, 這是由于久效磷農(nóng)藥通過促進(jìn)卵巢分化相關(guān)轉(zhuǎn)錄因子foxl2基因表達(dá), 并抑制精巢分化相關(guān)轉(zhuǎn)錄因子dmrt1基因表達(dá), 上調(diào)性腺芳香化酶表達(dá), 從而直接促進(jìn)斑馬魚卵巢的分化, 導(dǎo)致其性比向雌性偏離; 久效磷農(nóng)藥還能夠上調(diào)腦芳香化酶基因, 間接通過 HPG軸的調(diào)控作用, 進(jìn)一步導(dǎo)致斑馬魚雌性化。但這方面的研究由于實(shí)驗(yàn)設(shè)計(jì)、有機(jī)磷農(nóng)藥類型、實(shí)驗(yàn)物種等方面的差異,所得結(jié)果不盡一致[34]。例如, Tian等[35]研究報(bào)道, 孔雀魚(Poecilia reticulata)自出生至成年暴露于久效磷農(nóng)藥(0.01, 0.1 mg/L), 性別比例沒有變化, 推測(cè)原因在于性別分化的敏感度在不同物種間存在一定差異。

1.2 有機(jī)磷農(nóng)藥類雌激素效應(yīng)機(jī)制

1.2.1 干擾性激素的合成與轉(zhuǎn)化

性激素的合成轉(zhuǎn)化過程是在細(xì)胞的線粒體和滑面內(nèi)質(zhì)網(wǎng)中以膽固醇為底物進(jìn)行的一系列酶促反應(yīng),該過程的主要限速步驟主要有: 需要類固醇激素合成急性調(diào)節(jié)蛋白(steroidogenicacute regulatory protein,StAR)將合成底物膽固醇從線粒體外膜運(yùn)送至線粒體內(nèi)膜的轉(zhuǎn)運(yùn)過程; 膽固醇側(cè)鏈裂解酶(cholesterol side chain cleavage enzyme, CYP11A1)和 17α羥化酶(cytochrome P45017 alpha-hydroxylase, CYP17)催化膽固醇向T轉(zhuǎn)化的過程; 性腺芳香化酶P450 (cytochrome P450 aromatase, CYP19A)負(fù)責(zé)催化T芳構(gòu)化為E2的過程, 以及 11β-羥化酶催化 T向 11β-羥基睪酮轉(zhuǎn)化的過程; 最后由 11β-羥類固醇脫氫酶 II(11β-hydroxysteroid dehydrogenase type II, 11β-HSD2)作用生成 11-KT[36]。研究認(rèn)為StAR、CYP11A1、CYP17、CYP19A等均可作為環(huán)境雌激素發(fā)揮作用的主要靶位點(diǎn)[37]。

有機(jī)磷農(nóng)藥可以通過干擾性腺中 StAR活性或StARmRNA表達(dá)水平, 影響膽固醇被轉(zhuǎn)運(yùn)至線粒體內(nèi)膜, 導(dǎo)致性激素合成底物的減少, 使性激素合成水平急劇下降或性激素合成途徑中斷; 也可以誘導(dǎo)類固醇生成酶例如 17β-羥類固醇脫氫酶(17β-hydroxysteroid dehydrogenase, 17β-HSD) 、 P45017α和P450arom等基因表達(dá)的上調(diào)或下調(diào), 使酶活性的增強(qiáng)或減弱, 最終升高或降低機(jī)體的性激素水平, 影響機(jī)體正常的生殖功能。例如, 50 μg/mL樂果暴露MA-10小鼠睪丸間質(zhì)瘤細(xì)胞2~4 h, 導(dǎo)致StARmRNA表達(dá)水平顯著降低, 從而使進(jìn)入線粒體內(nèi)膜的膽固醇含量降低, T合成量顯著下降[38]。Bagchi等[39]證明, 喹硫磷能夠抑制胡鲇(ClariasBatrachus)性激素合成過程中 3β-HSD、17β-羥類固醇脫氫酶(17β-hydroxysteroid dehydrogenase,17β-HSD)的活性, 從而使雄激素合成過程受阻, 發(fā)揮類雌激素效應(yīng)。本實(shí)驗(yàn)室研究證明, 40%久效磷農(nóng)藥誘導(dǎo)雄性金魚(Carassiusauratus)性腺CYP19AmRNA表達(dá)量升高, 促進(jìn)了T向E2的轉(zhuǎn)化, 從而引發(fā)一系列生殖毒性。此外, 金魚性腺中StAR、P450scc、3β-HSD、P450c17、P45011β、11β-HSD2mRNA 表達(dá)水平受到抑制, 而20β-HSD、17β-HSD1mRNA 表達(dá)水平則上調(diào),說明有機(jī)磷農(nóng)藥發(fā)揮類雌激素效應(yīng)可能通過影響性激素合成過程中多種關(guān)鍵酶的表達(dá)水平, 導(dǎo)致血漿性激素含量的變化[40-41]。

此外, 部分有機(jī)磷農(nóng)藥能夠模仿內(nèi)源性激素與相應(yīng)受體(包括雄激素受體、雌激素受體)結(jié)合, 形成配體受體復(fù)合物, 隨后結(jié)合到細(xì)胞核DNA結(jié)合域的雌激素反應(yīng)元件上從而影響靶基因的轉(zhuǎn)錄, 進(jìn)而擾亂一系列激素依賴性生理過程[42]。

1.2.2 影響HPG軸對(duì)性激素的調(diào)控

性激素的合成過程還受到下丘腦-垂體-性腺軸(HPG軸)的影響, 其中垂體分泌的兩種促性腺激素(gonadotropic hormones, GtHs): 卵泡刺激素(folliclestimulating hormone, FSH)和促黃體激素(luteinizing hormone, LH)均能促進(jìn)性類固醇激素的合成過程[43];而下丘腦分泌的促性腺激素釋放激素(Gonadotropin-Releasing Hormone, GnRH)對(duì)于GtHs的分泌具有調(diào)節(jié)作用。因此, 有機(jī)磷農(nóng)藥可通過干擾GtHs、GnRH分泌改變性激素的水平; 反之也可通過反饋?zhàn)饔谜{(diào)節(jié)GtHs、GnRH的釋放。例如Laura等[44]發(fā)現(xiàn), 二嗪農(nóng)能夠通過干擾藍(lán)鰓太陽(yáng)魚(L.macrohirus)的 HPG 軸, 降低促性腺激素GtHs的生成, 進(jìn)而抑制卵巢中雌激素的合成。27 mg/kg馬拉硫磷使雄性大鼠下丘腦GnRH含量顯著降低, 導(dǎo)致血漿 FSH、LH水平下降, 最終抑制的T合成, 引起精子數(shù)量下降、能動(dòng)性減弱等生殖毒性[45]; 馬拉硫磷對(duì)印度囊鰓鯰(Heteropneustes fossilis)也具有類似的影響[46]。

2 有機(jī)磷農(nóng)藥的抗雄激素效應(yīng)及其機(jī)制

2.1 有機(jī)磷農(nóng)藥抗雄激素效應(yīng)

目前在體內(nèi)篩選實(shí)驗(yàn)中表現(xiàn)出抗雄激素效應(yīng)的有機(jī)磷農(nóng)藥見表2。有機(jī)磷農(nóng)藥發(fā)揮抗雄激素效應(yīng)能夠降低機(jī)體 T合成量, 而 T在雄性的生長(zhǎng)發(fā)育中起著決定性作用, 可促進(jìn)其第二性征出現(xiàn)、生殖器官發(fā)育并維持正常功能; 睪酮合成量受到影響最終會(huì)導(dǎo)致雄性精子數(shù)量、質(zhì)量下降, 前列腺、儲(chǔ)精囊等器官重量減輕[51], 并干擾雄激素依賴性分化進(jìn)程[52]。Viswanath等[47]報(bào)道, 毒死蜱、哌草磷能夠影響性激素合成過程中的關(guān)鍵酶(P450scc, 3β-HSD, 17β-HSD)的mRNA表達(dá)量, 導(dǎo)致Leydig細(xì)胞睪酮合成量顯著降低。Joshi等[53]以30 mg/kg甲基對(duì)硫磷暴露SD大鼠30 d, 暴露組大鼠睪丸、附睪、儲(chǔ)精囊和前列腺等雄激素依賴器官的質(zhì)量較對(duì)照組分別下降了33.75%、9.89%、0.34%、11.72%。大鼠Hershberger實(shí)驗(yàn)表明, 甲基毒死蜱在單獨(dú)使用時(shí)并不表現(xiàn)出抗雄激素效應(yīng), 但 50 mg/kg甲基毒死蜱與丙酸睪酮(testosterone propionate, TP)聯(lián)合暴露時(shí), 大鼠的前列腺、儲(chǔ)精囊等器官重量顯著下降, 證明甲基毒死蜱可通過拮抗TP的雄激素活性, 發(fā)揮了抗雄激素效應(yīng)[54]。此外, 雄激素(T、11-KT)具有調(diào)控雄激素受體(androgen receptor, AR)表達(dá)水平與功能的作用[55]。研究證明抗雄激素能夠通過下調(diào)雄激素含量, 導(dǎo)致肝臟、性腺等器官AR表達(dá)水平下降。例如, 敵敵畏暴露導(dǎo)致仔鼠陰莖皮膚組織中ARmRNA表達(dá)水平顯著降低[56]。另外, 環(huán)境抗雄激素黑名單中的利谷隆等也具有類似的作用[57]。

表2 發(fā)揮抗雄激素效應(yīng)的有機(jī)磷農(nóng)藥

有機(jī)磷農(nóng)藥發(fā)揮抗雄激素效應(yīng), 能夠影響雄性生殖行為, 導(dǎo)致雄性性欲降低; 暴露妊娠大鼠會(huì)對(duì)其產(chǎn)下的子代雄性產(chǎn)生不利影響。殺螟硫磷暴露雄性三刺魚(Gasterosteus aculeatus)26 d, 能夠?qū)е率苄奂に卣{(diào)控的腎 spiggin膠蛋白濃度下降, 影響三刺魚的筑巢和求偶行為[58]。0.2 μg/mL毒死蜱暴露孔雀魚(Poecilia reticulata)3 d, 能夠顯著降低雄性孔雀魚性欲, 減少交配次數(shù); 使雌性產(chǎn)仔數(shù)和子代存活率下降, 說明毒死蜱作為抗雄激素影響了孔雀魚的繁殖[59]。Turner等[60]則證明, 殺螟硫磷暴露妊娠大鼠, 導(dǎo)致產(chǎn)下的雄性子代大鼠出現(xiàn)生殖道發(fā)育異常, 表現(xiàn)為肛門到生殖器距離縮短, 從而影響子代大鼠的生殖能力。

由于有機(jī)磷農(nóng)藥抗雄激素效應(yīng)的研究還處于起步階段, 其發(fā)揮抗雄激素效應(yīng)所引起的生殖毒性以及對(duì)子代的影響等方面遠(yuǎn)不及類雌激素效應(yīng)研究的深入, 并且該領(lǐng)域大多以大鼠、小鼠為實(shí)驗(yàn)材料, 缺乏硬骨魚類、鳥類等物種的相關(guān)資料。另外, 有研究認(rèn)為同一種 EDCs可能對(duì)雄/雌性產(chǎn)生不同的內(nèi)分泌干擾效應(yīng)。例如, 氰戊菊酯對(duì)雄性大鼠血清 E2含量無影響, 但能極顯著降低血清和睪丸的T含量, 抑制精子發(fā)生[61-62]。沈蘇南[63]則發(fā)現(xiàn), 氰戊菊酯暴露導(dǎo)致雌性大鼠血漿E2含量顯著上升, T濃度無顯著性差異,則氰戊菊酯對(duì)雌性大鼠可能存在類雌激素效應(yīng)。殺螟硫磷、咪鮮胺等對(duì)雄/雌性大鼠的暴露實(shí)驗(yàn)也得到了類似的結(jié)論[64-65]。但是此類研究在有機(jī)磷農(nóng)藥中開展較少, 需要拓展探究。

2.2 有機(jī)磷農(nóng)藥抗雄激素效應(yīng)可能機(jī)制

目前較為公認(rèn)的環(huán)境抗雄激素大多通過影響AR信號(hào)通路來發(fā)揮作用。AR屬于核受體超家族中的類固醇受體, 由四個(gè)結(jié)構(gòu)域組成: N端轉(zhuǎn)錄激活區(qū)(NTD)、DNA結(jié)合區(qū)(DBD)、鉸鏈區(qū)以及配體結(jié)合區(qū)(LBD)[66-67]。通常 LBD 與熱休克蛋白連接, 雄激素進(jìn)入靶細(xì)胞后在胞漿內(nèi)作為配體與AR結(jié)合, 使AR構(gòu)型改變并解離熱休克蛋白, 從而增高與DNA親和力(亦稱作受體活化)。研究認(rèn)為具有抗雄激素效應(yīng)的有機(jī)磷農(nóng)藥, 例如敵敵畏、毒死蜱、哌草磷等均與AR呈現(xiàn)一定的親和力[47-48], 在不引起細(xì)胞毒性的情況下對(duì)AR表現(xiàn)出拮抗作用, 阻止體內(nèi)雄激素與AR結(jié)合, 抑制靶基因表達(dá)發(fā)揮抗雄激素效應(yīng)。環(huán)境抗雄激素與 AR結(jié)合所引起的構(gòu)型改變與正常的構(gòu)型改變存在差異, 這種差異抑制了AR的活化, 使AR無法進(jìn)入細(xì)胞核內(nèi)與DNA結(jié)合, 導(dǎo)致相關(guān)基因的轉(zhuǎn)錄翻譯無法進(jìn)行[68-69]。

正常情況下, 經(jīng)過活化的AR會(huì)轉(zhuǎn)移到細(xì)胞核內(nèi),在一系列共調(diào)節(jié)因子作用下以頭對(duì)頭或頭對(duì)尾方式形成同源二聚體, 識(shí)別靶基因上的相關(guān)應(yīng)答元件并與之結(jié)合, 進(jìn)而誘導(dǎo)轉(zhuǎn)錄活化、基因表達(dá), 促進(jìn)性分化和性發(fā)育[70-73]。在調(diào)控靶基因轉(zhuǎn)錄過程中, AR需通過共調(diào)節(jié)因子并發(fā)生蛋白質(zhì)-蛋白質(zhì)相互作用, 才能有效地影響轉(zhuǎn)錄。Kelce等[74]認(rèn)為環(huán)境抗雄激素可以通過影響共調(diào)節(jié)因子導(dǎo)致靶基因轉(zhuǎn)錄下調(diào), 例如烯菌酮(vinclozolin, V)和二氯二苯三氯乙烷(1,1-dichloro-2, 2-bis(p-chlorophenyl)ethylene, p, p′-DDE)在機(jī)體內(nèi)均能抑制由雄激素調(diào)節(jié)的prostateinsubunit C3基因表達(dá), 但是有機(jī)磷農(nóng)藥這方面的研究較為少見。

環(huán)境抗雄激素還可以影響HPG軸中某些環(huán)節(jié)的激素合成、分泌、激活、代謝來發(fā)揮作用。例如, 硫丹、氰戊菊酯暴露能通過抑制大鼠睪丸中17β-HSD、3β-HSD表達(dá)量影響 T的合成[75-76]。另有研究證明,甲基對(duì)硫磷能顯著降低長(zhǎng)尾鸚鵡血漿中FSH、LH、T的水平, 并引起生殖腺重量下降、曲細(xì)精管直徑減小等生殖毒性, 這主要是由于甲基對(duì)硫磷通過降低HPG軸中GtHs的分泌, 抑制性類固醇激素合成過程,導(dǎo)致T水平下降引發(fā)生殖毒性, 發(fā)揮抗雄激素效應(yīng)[77]。類固醇激素在水中的溶解度較小, 其轉(zhuǎn)運(yùn)過程依賴于運(yùn)載蛋白, 如睪酮需有睪酮結(jié)合球蛋白和白蛋白兩者運(yùn)輸才能到達(dá)靶細(xì)胞[70]。因此, 影響相關(guān)運(yùn)載蛋白也可以導(dǎo)致雄激素的分布和代謝發(fā)生改變, 從而產(chǎn)生抗雄激素作用, 但是在有機(jī)磷農(nóng)藥中這方面的相關(guān)研究較少。

3 展望

3.1 開發(fā)新的生物標(biāo)志物, 篩選具有抗雄激素效應(yīng)的有機(jī)磷農(nóng)藥

環(huán)境中的有機(jī)磷農(nóng)藥多以低劑量形式存在, 開發(fā)靈敏度高、特異性強(qiáng)的生物標(biāo)志物檢測(cè)抗雄激素類物質(zhì)具有重要意義。近年來, 睪丸抑制前列腺信使2(TRPM-2)、附睪aquaporin9(AQP9)蛋白、芳香化酶等受雄激素調(diào)控的基因和蛋白成為潛在抗雄激素生物標(biāo)志物[78-79]。然而, 有研究發(fā)現(xiàn), 這幾種指標(biāo)在不同的實(shí)驗(yàn)生物中對(duì)抗雄激素類物質(zhì)的反應(yīng)存在一定差異。例如, p, p′-DDE暴露大鼠, 能誘導(dǎo)芳香化酶蛋白顯著增加, 但在大鼠肝細(xì)胞實(shí)驗(yàn)中并沒有得到類似的結(jié)果[79]。因此, 今后需要大量研究驗(yàn)證以上潛在抗雄激素生物標(biāo)志物在不同物種中引起的反應(yīng)是否一致, 是否能夠達(dá)到理想檢測(cè)敏感度, 以及是否比現(xiàn)有的生物標(biāo)志物(spiggin蛋白、6α/15α-羥化酶比值)具有更廣泛的應(yīng)用范圍等。

3.2 從多個(gè)層面探究有機(jī)磷農(nóng)藥的抗雄激素效應(yīng)機(jī)制

在有機(jī)磷農(nóng)藥的抗雄激素效應(yīng)機(jī)制的研究中,研究者側(cè)重于由雄激素受體信號(hào)通路介導(dǎo)的抗雄激素效應(yīng)機(jī)制, 其他機(jī)制的研究相對(duì)較少。因此, 可以借鑒類雌激素機(jī)制的研究思路, 重點(diǎn)探究有機(jī)磷農(nóng)藥作為環(huán)境抗雄激素對(duì)HPG軸的影響以及對(duì)激素合成、轉(zhuǎn)運(yùn)的干擾。另外, 部分有機(jī)磷農(nóng)藥在不同實(shí)驗(yàn)條件下會(huì)表現(xiàn)出不同的內(nèi)分泌干擾效應(yīng)。例如, 殺螟硫磷在雄性大鼠的體內(nèi)實(shí)驗(yàn)中發(fā)揮抗雄激素效應(yīng),且在體外實(shí)驗(yàn)中能夠競(jìng)爭(zhēng)結(jié)合 AR[80-81]; 但單曉英等[82]發(fā)現(xiàn), 殺螟硫磷能夠?qū)е麓菩源笫笞訉m明顯增重,而大鼠子宮增重實(shí)驗(yàn)是評(píng)價(jià)化學(xué)物具有雌激素活性的經(jīng)典方法之一[83], 推測(cè)殺螟硫磷具有潛在的類雌激素效應(yīng)?？梢? 同一種有機(jī)磷農(nóng)藥在不同物種、不同性別、不同劑量的實(shí)驗(yàn)條件下所發(fā)揮的內(nèi)分泌干擾效應(yīng)差異較大。因此, 在進(jìn)行有機(jī)磷農(nóng)藥的抗雄激素效應(yīng)研究的過程中應(yīng)當(dāng)體內(nèi)、體外實(shí)驗(yàn)相結(jié)合, 選用分子、蛋白、器官、個(gè)體等多個(gè)層面的指標(biāo)對(duì)作用條件及機(jī)制進(jìn)行探索。

3.3 以對(duì)內(nèi)分泌系統(tǒng)的研究為基礎(chǔ), 探究與生殖系統(tǒng)、神經(jīng)系統(tǒng)的相互影響

有機(jī)磷農(nóng)藥作為類雌/抗雄激素對(duì)機(jī)體內(nèi)分泌功能具有直接的擾亂作用, 然而其對(duì)內(nèi)分泌系統(tǒng)的作用會(huì)間接導(dǎo)致對(duì)生殖細(xì)胞、生殖器官的毒性效應(yīng), 并最終導(dǎo)致機(jī)體的生殖能力下降。另外有研究證明, 有機(jī)磷農(nóng)藥暴露能夠抑制機(jī)體包括下丘腦在內(nèi)的多個(gè)腦部部位的乙酰膽堿酯酶活性[84-85], 下丘腦是機(jī)體HPG軸中重要的一環(huán), 其分泌的GnRH對(duì)GtHs、T、E2等激素具有調(diào)節(jié)作用, 說明有機(jī)磷農(nóng)藥的內(nèi)分泌干擾效應(yīng)與其神經(jīng)毒性存在一定聯(lián)系。因此, 研究有機(jī)磷農(nóng)藥的類雌、抗雄激素效應(yīng)可將內(nèi)分泌系統(tǒng)、生殖系統(tǒng)、神經(jīng)系統(tǒng)相結(jié)合, 明確各系統(tǒng)間的相互作用, 以便對(duì)其作用機(jī)制做出更為全面的闡釋。

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