Chapter 4: Factors Influencing Toxicity Flashcards

1
Q

What does it mean for a toxicant(s) to be additive? What is an example given in class?

A

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.

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2
Q

What does it mean for a toxicant(s) to be synergistic? What is an example given in class?

A

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.

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3
Q

What does it mean for a toxicant(s) to be antagonistic?

A

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).

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4
Q

What is functional antagonism?

A

2 toxicants produce opposite effects on a physiological function.

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5
Q

What is a chemical antagonism?

A

chemical reaction between the compounds leads to an inactivation that produces a less toxic effect.

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6
Q

What is dispositional antagonism?

A

alters the absorption, biotransformation, distribution or elimination of the toxicants.

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7
Q

What is receptor antagonism?

A

2 toxicants bind to the same receptor and interfere with the response.

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8
Q

What is potentiation? What is the example given in class?

A

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.

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9
Q

What can SNPs be used for?

A

Sequence differences between individuals can be measured using single nucleotide polymorphisms (SNPs) to identify different genotypes.

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10
Q

What are the two types of aldehyde dehydrogenase? Which one is used more?

A

one cytosolic (used less), one in the mitochondria of the liver (used more).

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11
Q

What mutation in the aldehyde dehydrogenase leads to acetaldehyde accumulation?

A

mutation in the mitochondrial form

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12
Q

What is the process of ethanol being degraded in the body?

A

ethanol —- alcohol dehydrogenase —> acetaldehyde —- aldehyde dehydrogenase —> acetate

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13
Q

How does resistance evolve in species?

A

mutations that alter the function of important detoxifying enzymes.

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14
Q

Define excretion/elimination rate

A

how long it takes to remove a compound from the tissue or body of an organism.

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15
Q

What is cross tolerance? What is an example of this?

A

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.

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16
Q

What is the resistance of a population or species?

A

a genetic basis for the ability of an organism to avoid a toxic
response when exposed to a toxicant
* Usually involves mutations and evolution!

17
Q

What is selective sweep?

A

A new beneficial mutation rises in frequency in a population.

18
Q

What is an example of resistance?

A

DDT binds to sodium channels and keeps them open, even when they should be closed.