TOXICOKINETICS Flashcards
What is toxicology
Study of poisons and their effects on humans or
Adverse effects of chemical or physical avens on living organisms
What was the state poison of the Greeks
Hemlock
A Chinese arrow poison
Aconite
Toxin Used both as a poison and an antidote
Opium
Who made the first attempt to classify poisons
Dioscorides
Who had an expeditious suicide poison hidden in his pen
Demosthenes
How did Cleopatra die
Falling on her asp
Who regularly ingested mixture of poisons to protect himself against assassination
Mithridates
Contribution of Hippocrates to toxicology
Talked about poisons Clinical toxicology principles pertaining to bioavailability in therapy and overdosage
Famous quote of Paracelsus pertaining to poisons
All things are poison and nothing is without poison only the dose makes a thing not a poison
Who is the modern father of toxicology
Mathieu Orfila
Why is Mathieu Orfila considered the father of modern toxicology
First toxicologist to use autopsy material SHS chemical analysis systematically as legal proof of poisoning
Branches of toxicology
Molecular
Environmental
Reproductive and Developmental
Regulatory
Clinical
How does toxicology contribute to physiology and pharmacology
Using toxic chemicals up understand physiological phenomena
What is a poison or toxicant
Interferes with homeostasis of organism or life processes of its cells but it’s one inherent qualities without acting mechanistically and irrespective of temperature
Hazardous vs Toxic
Hazardous - can cause harm
Toxic - produces adverse effects in living organisms
Poison vs Toxin vs Toxicant
Toxicant includes both toxins and poisons
Poisons - both natural and synthetic harmful substances
Toxin- natural only
Types of toxins
Zootoxin
Bacterial toxins - endotoxins and exotoxin
Phytotoxins
Mycotoxins
Toxicosis or poisoning
State of being poisoned
What is an ultimate toxicant
Chemical species that reacts with the endogenous target molecule
What species can act as the ultimate toxicant
Original chemical
Metabolite
Reactive oxygen or nitrogen species generated during biotransformation
Factors that promote delivery to target site
Absorption
Distribution toward target
Reabsorption
Toxication
Factors that reduce delivery to the target site
Presystemic elimination
Distribution away from the target
Excretion
Toxication
Intensity of a toxic effect depend primarily on ….. and …….
Concentration and persistence of the ultimate toxicant at the site of action
Which toxicant cause adverse effects at the site of exposure
Caustic and Corrosive toxicants
Movement of strongly acidic and basic substances and into urine and ph gradient in body systems occur by which method of absorption
Active transport
Factors affecting bioavailability
First pass metabolism - reduces
P glycoprotein activity - reduces
Enterohepatic circulation - enhances
Three types of capillaries
Sinusoïdal
Fenestrated
Continuous
Locations of fenestrated epithelium
Hepatic sinusoids
Renal peritubular capillaries
Examples of organs with specialized barriers
Brain
Placenta
Testicles
Examples of specialized barriers
Oocyte - multiple layers of granulosa cells
Spermatogenic cells - supported by tightly joined Sertoli cells
Which drugs bind to alpha 1 acid glycoprotein
Neutral and basic drugs
Which types of xenobiotics accumulate in the melanin containing cells off the retina and substantia nigra
Organic and inorganic cations
Polycyclic aromatic hydrocarbons
Which compounds bind to keratin
Thiol reactive metal ions and metalloid compounds
Which substances accumulate in adipocytes
Highly lipophilic substances such as chlorinated hydrocarbon insecticides
Where does lead accumulate in the body
Deposited in bone by substituting calcium in hydroxyapatite
Specialized membrane transport for arsénite, lead or barium ions and thallous ions
Arsénite - Aquaglyceroporin channeled
Lead or barium - VG Calcium channels
Thallous ion - Na/K/ATPase
Specialized membrane transport for alpha amanitin, ochratoxin and mercuric ion and lipoprotein bound toxicants
Alpha amanitin - NTCP
Ochratoxin and Mercuric ion - OAT1 and OAT3
Lipoprotein bound toxicants - Lipoprotein receptor
Substances that accumulate in cell organelles by ph trapping
Amphipathic compounds with a protonable amine group
Substances that accumulate in the cardiac mitochondria by electrophoretic trapping
Local Anaesthetics such as Tetracaine and Bupivacaine
Transporters that can export toxicant from cells
ABC transporters
P-glycoprotein
Which enzyme involved in biotransformation has a slow rate in cats
Glucuronyl transferase
Transporters involved in tubule secretion
SLC family- basolateral uptake
ABC carrier family - luminal uptake
Examples of Solute carrier family receptors
Organic acid transporters
Organic base transporters
OATP type (Organic anion transporting polypeptides)
Which substances are mostly secreted by renal tubules
Hydrophilic organic acids and bases
Factor affecting tubular reabsorption
Lipid solubility
Molecule size
Examples of substances not efficiently removed by liver and kidneys
Nonvolatile highly lipophilic chemicals
Polyhalogenated biphenyls and chlorinated hydrocarbon insecticides
The three processes for removing highly lipophilic nonvolatile substances
Excretion into mammary gland
Excretion into bile
Intestinal excretion into intestinal lumen
Morphine can be excreted into milk and amphetamine can be excreted into ———
Gastric juice
Four categories of enzyme systems
Hydrolysis
Reduction
Oxidation
Conjugation
Which enzymes metabolize over half the orally effective drugs
CYP2D6 and CYP3A4
In which cases does phase 2 precede phase 1 metabolism
Xenobiotics that undergo direct conjugation such as paracetamol
Enzymes responsible for intermediary ( endobiotic) metabolism
Endobiotic metabolising enzymes
Enzymes involved in drug metabolism
CYP450
Hepatic microsomal flavin contain
monooxygenases (MFMO or FMO)
Monoamine oxidase
Hydrolases
Which form of CYP450 absorbs maximally at 450nm and why
Reduced form due to the presence of bound CO
Location of CYP450
Smooth endoplasmic reticulum
How does CYP450 act as electron donor and acceptor
Changing the oxidation stage of bound iron between +2 and +3
Most abundant CYP450 enzymes in the liver
CYP3A4
CYP2Cx
Conjugation reactions
Glucuronidation
Sulfonation
Acetylation
Methylation
Conjugation with glutathione
Conjugation with amino acids
Which conjugation reactions produce lipophilic products
Methylation
Acetylation
Which conjugation reaction involve reactions with higher energy cofactors
Glucuronidation
Acetylation
Methylation
Sulfonation
Which conjugation pathways involve reactions with activated xenobiotics
Conjugation with glutathione and amino acids
Most conjugation enzymes are located in the cytosol except——-
UDP GT which are microsomal
Enzyme, cofactor and transferred group in glucuronidation
Enzyme —- UDP GT
Cofactor - UDP-GA
Transferred group - Glucuronic acid
Enzyme, cofactor and transferred group in Sulfonation
Enzyme - Sulfonyltranaferses
Cofactor - PAPS
Transferred group - Sulfone
Enzyme, cofactor and transferred group in acetylation
Enzyme - N acetyl transferase
Cofactor- Acetyl CoA
Transferred group - acetyl
Enzyme, cofactor and transferred group in methylation
Enzyme - methyl transferase
Cofactor - S-adenosylmethionine
Transferred group- methyl
Which amino acids make up glutathione
Glutamate
Cysteine
Glycine
Which conjugation has high capacity but low affinity
Glucuronidation
Which conjugation has low capacity but high affinity
Sulfonation
Which amino acid conjugate with their carbonyl group and produce toxic metabolites
Proline
Serine
Amino acids that conjugate with their amino ends producing benign metabolites
Taurine
Glutamine
Glycine
Which form of NAT is responsible for slow acetylators
Mutations in NAT2 gene
Slow acetylators exhibit higher incidence of adverse effects form which drugs
Clonazepam
Procainamide
Hydralazine
Sulfonamides
Isoniazid
Types of NAT
NAT1-Monomorphic
NAT2-Polymorphic
Compound ma which are substrates for acetylation
Aromatic amines
Hydrazines
Hydrazines
Types of acetylators
Slow and fast acetylators
Which type of acetylators are predisposed to bladder cancers
Slow acetylators
Which type of acetylators are more predisposed to colon cancers form earring red meat
Fast acetylators
Causes of bladder and colon cancer
Bladder- Bicyclic aromatic amines from cigarette
Colon- Heterocyclic aromatic amines from red meat
Substrates for the various methyltransferases
COMT- dopamine, norepinephrine, METHYLDOPA
PNMT- norepinephrine to epinephrine
HNMT- Drugs that contain an imidazole ring
NNMT- Serotonin and Tryptophan
TPMT- Aromatic and Heterocyclic sulfhydryl compounds
Examples of thiopurine drugs
Azathioprine
6-Mercapptopurine
Thioguanine
Examples of reactive nucleophiles
HCN
CO
H2S
N2
Examples of substances that can produce superoxide radical
Paraquat
Nitrofurantoin
Doxorubicin
Why avoid iron supplement during infection
Iron is involve in the Fenton reaction which generates the hydroxyl radical
Methods for détoxication of électrophiles
Conjugation with glutathione spontaneously or facilitated by glutathione s transferases
Detoxification of free radicals
Superoxide dismutase
Catalase
Glutathione peroxidase
Forms of Superoxide dismutase and the location
Cu and Zn SOD- Cytosolic
Mn SOD- Mitochondrial
Examples of antioxidants which detoxify peroxyl radicals
Glutathione
Vitamin E
Vitamin C
Uric acid
Examples of proteins that contain transition metal centers
Myoglobin
Hemoglobin
Cytochrome C
In which part of the body is uric acid an antioxidant and where is it a prooxidant
Antioxidant in plasma
Prooxidant in cells
Why is cysteine not given in the pure form but given as N acetyl cysteine
Cysteine causes toxicity
Which enzyme is incapacitated by ONOO-
Mn-SOD