Chapter 4: Factors Influencing Toxicity Flashcards
What does it mean for a toxicant(s) to be additive? What is an example given in class?
The total amount of toxicity is the sum of the toxicities of the compounds (2 + 2 = 4).
organophosphate insecticides have a similar structure and both cause toxicity by inhibiting acetylcholinesterase. Taking a certain amount of one is pretty much the equivalent of taking the same amount of the other.
What does it mean for a toxicant(s) to be synergistic? What is an example given in class?
The total amount of toxicity is greater than the sum of the
toxicities of the compounds (2 + 2 = 8).
Workers exposed to asbestos have an increased risk of lung
cancer by 20 times, smokers have a 26 times increase in risk. The combination of the two increases the risk to 400 times.
What does it mean for a toxicant(s) to be antagonistic?
The total amount of toxicity is less than the sum of the
toxicities of the compounds (2 + 2 = 1; 2 +2 = 3; 2 + 2 = 0.5).
What is functional antagonism?
2 toxicants produce opposite effects on a physiological function.
What is a chemical antagonism?
chemical reaction between the compounds leads to an inactivation that produces a less toxic effect.
What is dispositional antagonism?
alters the absorption, biotransformation, distribution or elimination of the toxicants.
What is receptor antagonism?
2 toxicants bind to the same receptor and interfere with the response.
What is potentiation? What is the example given in class?
A non-toxic chemical (at the levels normally administered or
encountered) makes a different toxicant even more toxic.
Warfarin is an anticoagulant (prevents blood clotting). It binds to albumin (a sticky protein) in the blood which keeps its “free”
concentration down. If a low (non-toxic) dose of another drug/toxicant that is also carried by albumin is administered, the warfarin gets displaced off the albumin and can quickly reach toxic levels in the blood.
What can SNPs be used for?
Sequence differences between individuals can be measured using single nucleotide polymorphisms (SNPs) to identify different genotypes.
What are the two types of aldehyde dehydrogenase? Which one is used more?
one cytosolic (used less), one in the mitochondria of the liver (used more).
What mutation in the aldehyde dehydrogenase leads to acetaldehyde accumulation?
mutation in the mitochondrial form
What is the process of ethanol being degraded in the body?
ethanol —- alcohol dehydrogenase —> acetaldehyde —- aldehyde dehydrogenase —> acetate
How does resistance evolve in species?
mutations that alter the function of important detoxifying enzymes.
Define excretion/elimination rate
how long it takes to remove a compound from the tissue or body of an organism.
What is cross tolerance? What is an example of this?
where an individual becomes tolerant to different similar toxicants because of exposure to one compound.
Example: Heroin users may show increased tolerance to other opioids. They elicit a response through the same cellular receptor.
