Principles of Toxicology III Flashcards
A bodies natural method for detoxifying and/or removing foreign substances (xenobiotics) involves…
Biotransformation/metabolism
Excretion
What is a xenobiotic?
Most are..
A foreign substance. Most are.. -weak acids or bases -Ionization depends on pH -lipid soluble when unionized
****What are the organs MOST commonly involved in metabolism/biotransformation..
LIVER and GI
What are the advantages of the LIVER and GI for metabolism and biotransformation?
- Receives the greatest fraction of total cardiac output after the lungs.
- Contains the widest breadth of metabolic enzymes.
- Liver has significant endothelial surface for filtration of blood.
- Liver can distribute products to blood or bile for excretion via the kidneys or GI tract.
What organ in the body receives 100% of cardiac output?
LUNGS
Upper and lower respiratory tracts have also a large amount of surface area for absorption. Act to metabolize aerosolized xenobiotics. Thick nasal conchae but lungs as well- receives 100% of cardiac output.
What are phase I reactions?
3 types: oxidation, reduction and hydrolysis.
act to..
-increase the polarity of metabolites
-provide reactive sites for phase II enzymes
What are phase II reactions?
Conjugation reactions that couple xenobiotics to other molecules
act to..
-increase molecular weight (glutathione, methyl groups are added)
-increases polarity of metabolites
Both phase I and phase II reaction..
Modify the biological activity of parent compounds.
What are the ways that drugs can be changed in the body?
- Once it is absorbed by an animal.. Can pass straight through to the urine or feces.
- Can have a drug in-effected by phase I.. Conjugated by phase 2.
- Most commonly* phase 1 changes the molecule, the products conjugated and eliminated.
- Lipophilic molecule + enzymes => gets changed to hydrophilic and is excreted.
Chemical inactivation of a parent compound generally means…
loss of parent activity.
not the same as loss of ANY activity!
Biotransformation can..
REDUCE
ENHANCE or
COMPELETLY CHANGE biological activity.
Phase II conjugation reactions cause..
large changes (MW and polarity) usually resulting in the COMPLETE LOSS of activity.
Phase I reactions can…
create molecules with modified activity..
- don’t increase the polarity as much as in phase II reactions.
- modify reactive groups in a molecule instead of large MW changes.
- metabolites are still capable of crossing membranes.
Cellular distribution of phase I and II enzymes can be… (2)
microsomal or non-microsomal
Cellular distribution of phase I and II enzymes
MICROSOMAL
Derived from the endoplasmic reticulum.
*Means the way the cells are processed. These detoxifying enzymes.
Cellular distribution of phase I and II enzymes
NON-MICROSOMAL
Derived from the cytoplasm
Phase I
Microsomal/ER
Esterase's Epoxide hydrolase (inducible) Flavin monooxygenase (inducible) Cytochrome P450s (inducible)
Phase I
Microsomal/ER
Glucuroniation (inducible)
Glutathione conjugation (inducible)
Glycine conjugation
Methylation
Phase I
Cytoplasmic
Esterases Epoxide hydrolase (inducible) Peptidase Alcohol dehydrogenase aldehyde dehydrogenase
Phase II
Cytoplasmic
Sulfation
Glutathione Conjugation (inducible)
Acylation
Methylation
Phase I
Mitochondrial
Monamine oxidase
aldehyde dehydrogenase