外源化学物在体内的生物转运与生物转化

第三章 外源化学物在体内的生物转运与生物转化,Toxicokinetics (毒物代谢动力学 ) how the body handles poisons Toxicodynamics (毒物效应动力学) what poisons may do to the body,Toxicokinetics refers to the processes of absorption, distribution, elimination, and metabolism of a toxicant.TK describes the changes of the concentrations of a compound in the organism over time.Toxicodynamics refers to the actions and interactions of the toxicant within the organism and describes processes at organ, tissue, cellular, and molecular levels.TD describes the dynamic interactions of a compound with a biological target and its downstream biological effects,Biotransportation (生物转运)Biotransformation (生物转化),Toxicokinetics (Exposure & fate of chemicals),disposition - Absorption- Distribution- Metabolism- Excretion,Summary of the disposition of toxicants as determined by absorption, distribution, and excretion in the body,外源化学物在体内的生物转运,Xenobiotic,Excretion,一、生物膜与生物转运二、吸 收三、分 布 四、排 泄,Biomembrane The Fluid Mosaic Model,卫生毒理学系,Membrane transport,卫生毒理学系,被动转运(passive transport)简单扩散(simple diffusion)滤过(filtration),特殊转运(special transport) 主动转运(active transport)易化扩散(facilitated diffusion)膜动转运(cytosis)。,The differences between diffusionand active transport,卫生毒理学系,Passive transport,Diffusion across a plasma membrane in which the cell expends no energy the diffusion of oxygen and carbon dioxideosmosis of waterfacilitated diffusion,卫生毒理学系,Fick定律,RKA（c1c2）/ d,R为扩散速率，K为特定外源化学物的扩散常数，A为生物膜的面积，（c1c2）为生物膜两侧的浓度梯度，d为生物膜的厚度,脂/水分配系数(lipid/water partition coefficient),Passive Processes,Water diffusion: osmotic pressure,卫生毒理学系,Facilitated diffusion,卫生毒理学系,Facilitated diffusion,卫生毒理学系,Active transport,卫生毒理学系,Three Types of Proteins for Active Transport,卫生毒理学系,uptake of amino acids from the intestine,sodiumpotassium pump,calcium-binding protein,Primary active transportsodiumpotassium (Na+K+) pump,卫生毒理学系,Secondary active transport,卫生毒理学系,Xenobiotic transporters,卫生毒理学系,Major ABC Transporters Involved in Xenobiotic Disposition,MDR1/P-gp多药耐受蛋白或P-糖蛋白 MRP(multiresistant drug protein)多耐受药物蛋白,ATP binding cassette (ABC),they play important roles in absorption from the GI tract and elimination into bile or into urine for a diverse array of xenobiotics. They are also critical to maintaining the barrier function of numerous tissues sites including the bloodbrain barrier, the bloodtestis barrier, and the maternalfetal barrier or placenta.,P-gp,卫生毒理学系,Xenobiotic transporters,卫生毒理学系,Major Members of the Solute Carrier Transporters Involved in Xenobiotic Disposition,Solute carrier (SLC),有机阴离子转运多肽,有机阴离子转运蛋白,有机阳离子转运蛋白,肽类转运蛋白,肉(毒)碱,divalent metal transporter (DMT)二价金属离子转运蛋白,DMT1previously known as NRAMP2(natural resistance-associated macrophage protein ), was first identified in 1995 in a screening for homologues of NRAMP1, a protein involved in host defense against several types of infection. Subsequently, it was referred to as divalent cation transporter (DCT1) because of its ability to transport cations, such as Zn2+, Mn2+, Co2+, Cd2+, Cu2+, Ni2+, Pb2+ and Fe2+,卫生毒理学系,Membrane Transporters in ToxicologyToxicol. Appl. Pharmacol. 204 , 197 360 , 2005 ./science/journal/0041008X,卫生毒理学系,DMT,Endocytosis and Exocytosis,卫生毒理学系,endocytosis胞吞: phagocytosis 吞噬pinocytosis 胞饮receptor-mediated endocytosis,Receptor-mediated endocytosis,卫生毒理学系,Pinocytosis胞饮,Phagocytosis,吸 收,吸收（abosorption）是外源化学物从机体的接触部位透过生物膜屏障进入血液的过程。,卫生毒理学系,Skin (dermal),Lung (inhalation),Oral (gut),Injection,经胃肠道吸收,胃肠道是外源化学物的主要吸收途径吸收可在任何部位进行，但主要在小肠吸收方式：主要是通过简单扩散，还可以通过滤过、胞饮或吞噬和主动转运系统,卫生毒理学系,胃肠道的酸碱度外源化学的分子结构及理化性质胃肠道的蠕动情况 胃肠道中的某些物质及菌丛 芳香硝基化合物还原成芳香胺（致癌、致甲状腺肿）,影响胃肠道吸收因素,卫生毒理学系,经胃肠道吸收,卫生毒理学系,Gastric pH and Emptying Time in Dogs and Humans,经胃肠道吸收,卫生毒理学系,pH of the Gastrointestinal Contents of Various Species,Intestinal processing and absorption of dietary components,卫生毒理学系,经胃肠道吸收,经胃肠道吸收的外源化学物通过门静脉系统首先达到肝脏，进行生物转化后，再进入体循环，这种现象称为首过消除（first pass elimination）,卫生毒理学系,卫生毒理学系,肺泡生理结构和特点 不经过肝脏的生物转化，直接进入体循环而分布全身 主要通过简单扩散,气体、蒸气与气溶胶经肺吸收的影响因素不同,经呼吸道吸收,卫生毒理学系,卫生毒理学系,肺泡,气态毒物的浓度即毒物在吸入空气中的分压（或称张力）气态毒物在血液中的溶解度血/气分配系数（blood/gas partition coefficient） 肺泡的通气量和血流量肺泡通气量与血流量的比值称为通气 /血流比值,卫生毒理学系,气态毒物经肺吸收的影响因素,卫生毒理学系,直径为5m或更大的颗粒物通常因惯性冲击而沉积于鼻咽部,2m5m的颗粒物主要依靠重力沉降于气管、支气管区域,直径在1m及以下的颗粒物可以到达肺泡并被吸收入血,气溶胶毒物经肺吸收的影响因素,水溶性也影响吸收,穿透阶段：外源化学物透过皮肤表皮，即角质层的过程吸收阶段：由角质层进入乳头层和真皮， 并被吸收入血吸收方式：简单扩散,卫生毒理学系,经皮肤吸收,皮肤组织学结构示意图（1）,卫生毒理学系,皮肤组织学结构示意图（2）,卫生毒理学系,环境污染物的皮肤吸收,卫生毒理学系,环境污染物,表皮,毛囊、汗腺、皮脂腺,表皮角质层, 阻止MW300,连接角质层, 阻止水溶性物质,基底膜,血液,理化性质：脂/水分配系数接近于1，易被 吸收进入血液皮肤血流速度和出汗状况皮肤完整性：如皮肤破损，破坏表皮角 质层屏障作用，外源化学物可以直接进 入吸收相人体不同部位表皮的厚度不同、角质层 厚度不同，所以外源化学物的穿透速度 有别 汞等一些金属及化合物，可以经过毛囊、皮脂腺和汗腺直接进入血液种属差异 大鼠和兔通透性好，豚鼠、猪和猴的皮肤通透性与人接近,卫生毒理学系,经皮肤吸收的主要影响因素,经眼吸收：局部作用先于全身作用经静脉、腹腔、皮下和肌内注射,卫生毒理学系,经其它途径吸收,the process in which a chemical agent translocates throughout the body,Blood carries the agent to and from its site of action, storage depots, organs of transformation, and organs of eliminationRate of distribution dependent uponblood flowcharacteristics of toxicant (affinity for the tissue, and the partition coefficient)Distribution may change over time,卫生毒理学系,分 布Distribution,卫生毒理学系,Distribution:Storage and Binding,Storage in Adipose tissue脂肪组织-Very lipophylic compounds (DDT) will store in fat. Rapid mobilization of the fat (starvation) can rapidly increase blood concentrationStorage in Bone骨骼组织-Chemicals analogous to Calcium-Fluoride, Lead, StrontiumBinding to Plasma proteins血浆蛋白质-can displace endogenous compounds. Only free is available for adverse effects or excretion肝脏和肾脏,双重毒理学意义,血脑屏障(blood-brain barrier)胎盘屏障(placental barrier)其他屏障,卫生毒理学系,分 布：特殊的屏障,BloodBrain Barrier,卫生毒理学系,Schematic model showing the xenobiotic transporting systems that contribute to the bloodbrain barrier.,Schematic model showing the xenobiotic transporting systems that contribute to the bloodcerebral spinal fluid barrier,卫生毒理学系,血脑屏障,血脑屏障结构特点： 中枢神经系统的血管内皮细胞结合紧密，细胞间没有或仅有很小的孔隙 脑毛细血管内皮细胞具有多药耐受(mdr)蛋白 中枢神经系统的毛细血管大部分被星形胶质细胞所包围 中枢神经系统组织间液的蛋白质含量较机体其他部位低,Not an absolute barrierCaffeine (small)Methylmercury cysteine complexLipids (brain is a ball of fat),胎盘屏障,卫生毒理学系,合体滋养层,细胞滋养层和基膜,绒毛结缔组织,绒毛毛细血管,至今还没有肯定胎盘在防止毒物从母体进入胚胎的特殊作用。如致畸物可经过胎盘引起胚胎畸形，有些致癌物也具有经胎盘致癌作用。,大部分外源化学物透过胎盘的机理是简单扩散，而胚胎发育所必需的营养物质，则通过主动转运而进入胚胎。,Toxicants are eliminated from the body by several routes,Urinary excretionExhalationBiliary Excretion via Fecal ExcretionCSFMilkSweatSaliva,卫生毒理学系,排 泄 Excretion,经肾脏,卫生毒理学系,主要排泄机理 肾小球滤过肾小球简单扩散肾小管主动转运,外源性化学物由肝实质细胞进入胆汁而排泄 外源性化学物从胆汁进入小肠后，可能有两条去路：1)直接排出体外；2)肠肝循环,卫生毒理学系,经粪便,肠肝循环(enterohepatic circulation) ：是指部分外源化学物在生物转化过程中形成结合物，并以结合物的形式排出在胆汁中；肠内存在的肠菌群以及葡萄糖苷酸酶，可将部分结合物水解，则使外源化学物又重新被吸收的过程。毒理学意义,经肝胆排出和肝肠循环,卫生毒理学系,毒物,肠道,全身其他脏器,胆汁,贮存,代谢,肝脏,消化道,血液,粪 便,解毒,排出体外,消化道不吸收,其排泄速度与血/气分配系数成反比，即血气分配系数越大，排泄越慢与吸收速度相反,卫生毒理学系,经肺排泄,卫生毒理学系,其它排泄途径,乳汁排出 脂溶性毒物如DDT、PCB、多溴联苯和TCDD等;化学性质与钙类似的金属（如铅）以及能与钙形成配位体的螯合剂。,汗腺和唾液腺排出 非解离态、脂溶性毒物,头发和指甲排出 砷、汞、铅、锰等,脑脊液 主动转运参与脑脊液排出毒物的过程,Metabolism: adverse effect depends on the concentration of active compound at the target site over time,The process by which the administered chemical (parent compounds) are modified by the organism by enzymatic reactions.1o objective-make chemical agents more water soluble and easier to excretedecrease lipid solubility - decrease amount at targetincrease ionization - increase excretion rate - decrease toxicityBioactivation-Biotransformation can result in the formation of reactive metabolites,卫生毒理学系,外源化学物在体内的生物转化,卫生毒理学系,Metabolism,Decrease biological activity2) Increase excretability,General Scheme of Xenobiotic Biotransformation,Lipophilic Hydrophilic(parent compound) (metabolite),Phase I Phase II(oxidative) (synthetic),Metabolites,Metabolites,BioactivationDetoxification,Detoxification,polarityfunctionality,sizeionizationwater solubilityIncrease excretability,生物转化Biotransformation,Key organs in biotransformationLIVER (high)Lung, Kidney, Intestine (medium)Others (low)Biotransformation PathwaysPhase I-make the toxicant more water solublePhase II-Links with a soluble endogenous agent (conjugation),卫生毒理学系,相反应发生的部位,卫生毒理学系,Location of CYPs in the cell,卫生毒理学系,卫生毒理学系,Catalytic cycle of cytochrome P450,1. Hydroxylation of an aliphatic or aromatic carbon;2. Epoxidation of a double bond;3. Heteroatom (S-, N-, and I-) oxygenation and N-hydroxylation;4. Heteroatom (O-, S-, and N-) dealkylation;5. Oxidative group transfer;6. Cleavage of esters;7. Dehydrogenation.,CYPs,卫生毒理学系,Nomenclature of cytochromes P450. Members of the same family share 40% amino acid homology, and members of the same subfamily share 55% amino acid homology.there are 57 human genes and 102 mouse genes.Italics are used to designate genes, whereas mRNAs and proteins are nonitalicized by convention.http:/www.imm.ki.se/CYPalleles/ /CytochromeP450.html,Reaction catalysed by cytochrome P450,卫生毒理学系,hydroxylation of aliphatic & aromatic carbonsN-, O- and S-dealkylation N-oxidation & N-hydroxylation Sulfoxidation desulfuration oxidative deamination oxidative dehalogenation epoxidation,卫生毒理学系,卫生毒理学系,脂肪族羟化,O,八甲磷,N-羟甲基八甲磷,芳香族化合物的羟化,卫生毒理学系,西维因,1-羟基-1-萘-N-甲基氨基甲酸酯,1-萘-N-羟基氨基甲酸酯,苯,环氧化,酚,分子重排,（非酶促反应）,胺类化合物的N-羟化,卫生毒理学系,胺类化合物的N-氧化,卫生毒理学系,黄素加单氧酶Flavin - Containing Monooxygenase (FMO),卫生毒理学系,N OxidationNicotinedimethylaniline二甲基苯胺imipramine丙咪嗪S OxidationThiobenzamide硫代苯甲酰胺, phorate甲拌磷thiourea硫脲P OxidationDiethylphenylphosphine二乙基苯膦DesulfurationFonofos地虫磷,Prostaglandin Synthetase (PGS) Cooxidation,卫生毒理学系,Dehydrogenation：Acetaminophen醋氨酚, benzidine联苯胺, DES己烯雌酚, epinephrineN Demethylation：Dimethylaniline二甲基苯胺, benzphetamine苄非他明, aminocarb灭害威Hydroxylation：Benzo a pyrene, 2 - aminofluorene氨基芴, phenylbutazone保泰松Epoxidation：7,8 - Dihydrobenzo a pyreneSulfoxidation：Methylphenylsulfide甲基苯基硫醚，茴香硫醚Oxidations：FANFT（N-4-(5-硝基-2-呋喃)2-噻唑甲酰胺）, ANFT（2-氨基一4-(5硝基一2-呋喃) 噻唑）, bilirubin胆红素,还原反应 reduction,主要是细胞色素P450和黄素蛋白酶。肠道菌群还原酶的活性较高(1) 偶氮还原和硝基还原 主要由肠道菌群催化。细胞色素P450、醛氧化酶和NADPH醌氧化还原酶（DT-黄素酶，肝细胞液）(2) 羰基还原 羰基还原酶是NADPH依赖酶，分布于血液及肝、肾、脑等组织的细胞液中，主要催化某些醛类还原为伯醇或酮类还原为仲醇的反应。 (3) 醌还原(4) 脱卤反应 脂肪族化合物脱卤包括3种机制，即还原脱卤、氧化脱卤和脱氢脱卤。,卫生毒理学系,偶氮还原和硝基还原Azo- and Nitro-Reduction,卫生毒理学系,羰基还原Carbonyl Reduction,卫生毒理学系,氟哌啶醇,水合氯醛,醌还原Quinone Reduction,卫生毒理学系,自氧化,还原脱卤Reductive dehalogenation,卫生毒理学系,水解反应Hydrolysis,包括酯酶、酰胺酶、肽酶和环氧化物水化酶，广泛存在于血浆、肝、肾、肠和神经组织中。(1) 酯酶和酰胺酶 可水解具有羧酸酯、酰胺、硫酯、磷酸酯和酸酐等功能基团的外源化学物。酯类可被水解为醇和酸，酰胺可被水解为酸和胺，硫酯可被水解为酸和硫醇。酯酶3类：A-酯酶可以水解有机磷酸酯 如对氧磷酶B-酯酶则为有机磷酸酯所抑制 如羧酸酯酶和胆碱酯酶C-酯酶既不能水解有机磷酸酯也不能被其抑制。(2) 肽酶 氨基肽酶，羧基肽酶，内肽酶肽酶可水解相邻氨基酸之间的酰胺键，故功能上属于酰胺酶。,卫生毒理学系,水解反应Hydrolysis,(3) 环氧化物水化酶(epoxide hydrolase, EH) 广泛存在于肝、睾丸、卵巢、肺、肾、皮肤、肠、胸腺、脑和心脏等全身组织中，可催化环氧化物水解生成具有反式构型的邻位二醇。在哺乳动物体内有5种EH，但具有代谢外源化学物作用的只有：微粒体环氧化物水化酶(microsomal epoxide hydrolase，mEH)可溶性环氧化物水化酶(soluble epoxide hydrolase，sEH) 多数情况下，EH与细胞色素P450分布保持一致。Why？EH的催化作用与底物的空间构型有关如苯并(a)芘-7,8-二氢二醇-9,10-环氧化物所具有的湾区结构即有此种功能，可免受EH水解而发挥其致突变、致癌作用。,卫生毒理学系,卫生毒理学系,正苯醌,儿茶酚,其他I相反应,Alcohol Dehydrogenase (ADH ) Oxidations： Ethanol, methanol, isopropanol, glycols, glycol ethers乙二醇醚,(2 - butoxyethanol 2-丁氧基乙醇)Reductions：Aldehydes and ketonesAldehyde Dehydrogenase (ALDH )Oxidations：Aldehydes from alcohol and glycol oxidationsMolybdenum Hydroxylases钼水解酶 (Aldehyde Oxidase, Xanthine Oxidase黄嘌呤氧化酶)Oxidations：Purines, pteridine蝶啶, methrotrexate甲氨蝶呤，quinolones喹诺酮, 6 - deoxycyclovir去氧环鸟苷Reductions：Aromatic nitro compounds芳族硝基化合物, azo dyes偶氮染料, nitrosamines亚硝胺类, N oxides氮氧化物, sulfoxides亚砜类Esterases and AmidasesParaoxon对硝苯磷酯, dimethoate乐果, phenyl acetate乙酸苯酯Epoxide HydrolaseBenzo( a )pyrene epoxide, styrene oxide氧化苯乙烯DDT Dehydrochlorinasep,p - DDTGlutathione ReductaseDisulfiram二硫化四乙基秋兰姆,卫生毒理学系,卫生毒理学系,Ethanol,相反应Conjugation Reactions,卫生毒理学系,glycosylated, sulfated, methylated, and acetylated conjugates,Type I,Type II,peptide and glutathione conjugation,Structures of cofactors for phase II biotransformation,卫生毒理学系,II相反应发生的部位,卫生毒理学系,Conjugation Reactions,卫生毒理学系,UDPGT,SULT,GST,NAT,葡萄糖醛酸结合 Glucuronidation,卫生毒理学系,结合产物具有高水溶性，可通过胆汁排出或随尿液排泄。但经胆汁排出部分可被肠道下段菌群的- 葡萄糖醛酸酶作用而发生水解，毒物被重新吸收，进行肠肝循环。,卫生毒理学系,双氯芬酸,Bioactivation,硫酸结合 sulfation,卫生毒理学系,反应产物为高水溶性的硫酸酯，主要经尿排泄，少部分随胆汁排出。,卫生毒理学系,Bioactivation,黄樟脑,谷胱甘肽结合glutathione conjugation,卫生毒理学系,GSH结合物具有极性和水溶性，可经胆汁排出，也可随体循环转运至肾脏并经一系列酶促反应转变为硫醚氨酸衍生物，由尿排泄。,马来酸二乙酯,丙内酯,4-硝基喹啉N-氧化物,卫生毒理学系,GSH结合被认为是亲电子剂解毒的一般机制,Examples of glutathione conjugation of electrophilic heteroatoms,甲基化反应 methylation,卫生毒理学系,Nicotinamide N methyltransferaseHistamine methyltransferasenoradrenaline methyltransferase,Catechol - O - methyltransferase (COMT)Phenol O - methyltransferase (POMT),Thiol methyltransferase,甲基化反应产物水溶性通常不如母体，不利于从机体消除，但毒性普遍降低,乙酰化作用 acetylation,卫生毒理学系,aromatic amides芳香酰胺(RNHCOCH3),hydrazides酰肼(RNHNHCOCH3),hydrazine group 肼(RNHNH2),aromatic amine 芳香胺(RNH2),low NAT2 activity increases the risk of bladder, breast, liver and lung cancers, and decreases the risk of colon cancer, whereas low NAT1 activity increases the risk of bladder and colon cancers and decreases the risk of lung cancer,NAT1 is expressed in most tissues of the body, whereas NAT2 is expressed mainly in the liver and the intestine. However, most (but not all) of the tissues that express NAT1 also appear to express low levels of NAT2, at least at the level of mRNA. NAT1 and NAT2 also have different but overlapping substrate specificities.,卫生毒理学系,磺胺甲噁唑,对氨基水杨酸,4-氨基苯甲酸,异烟肼,磺胺甲嘧啶,氨苯砜,Bioactivation,乙酰化作用的利弊取决于解毒与活化反应的相对速度。如前致癌物芳香胺类的乙酰化是解毒反应，但芳香胺的N-羟化产物也是NAT的底物，可形成N,O-乙酯并最终生成氮宾离子，此为代谢活化。,氨基酸结合amino acid conjugation,卫生毒理学系,羧酸酰基-CoA合成酶N-酰基转移酶解毒过程芳香羟胺氨酰基-tRNA合成酶活化反应,遗传因素物种、性别、年龄、生理和营养状态等，表现为毒物代谢酶的种类、分布、数量和活性差别。代谢酶的遗传多态性。环境因素干扰代谢酶的合成与催化过程代谢酶的诱导和抑制就是最主要的表现形式,卫生毒理学系,影响生物转化的某些因素,毒物代谢酶的遗传多态性,遗传多态性(genetic polymorphism)系指在群体中出现了频率大于1%的多种等位基因形式。,卫生毒理学系,卫生毒理学系,卫生毒理学系,SNP,卫生毒理学系,毒物代谢酶的诱导和阻遏,酶的诱导（enzyme induction）指许多外源化学物可引起某些代谢酶的合成增加并伴有活力增强。凡具有诱导效应的毒物称为诱导剂(inducer)。诱导剂分为双功能和单功能两类酶的阻遏（enzyme repression）指对某些代谢酶