Lecture 2 - Effect of toxins, xenobiotics

What does the effect of the toxin depend on?

Organism’s maturity, vulnerability (adult vs child)

What is toxicity

The ability of a substance to cause harm

What is exposure

The process by which an organism comes into contact with a substance

What is the effect

Responce of an organism to exposure.

What are the 3 groups we classify acute toxicity by?

Strongly toxic, toxic, harmful

When is a substance **strongly toxic?**

When is a substance **toxic?**

25-200mg/kg

When is a substance **harmful**?

200-2000mg/kg

What is a **threshold** level?

The effect of a substance is observed above a certain dose

What type of substances do not have a threshold + example?

Carcinogenic substances (TCDD)

How can different substances (xonobiotics) have different effects by location?

point of entry, distribution through body into the system

What are the different ways toxins act in the body?

Direct toxicity, Biochemical, Immunotoxic, Carcinogenic, Mutagenic, teratogenic, Organ specific

What is the __direct toxic__ level

A substance acts at a critical location in an organism

What is __biochemical__ toxicity?

The substance affects some biochemical action and affects some vital function

What is ***competitive*** inhibition?

When the inhibitor binds to an active site of an enzyme, slowing down reactions (cempetition between the inhibitor and the substrate)

What is ***non-competitive*** inhibition?

The inhibitor binds to an enzyme elsewhere, alters it and is unable to perform its function, reaction stops.

What is the __immunotoxic__ effect?

Response to a toxin by changes in the immune system (eg. allergic reaction, immuno-suppression)

What is immuno-suppression?

Suppression of the body’s immune system and altering the ability to fight infections.

What are the basic components of the immune system?

lymphatic system, white blood cells (peripheral leukocytes)

How does an allergic reaction work?

Chemical not recognised as antigen, Binds to physiological protein molecules and chemically alters them, production of antibodies

What is __carcinogenicity__?

Mutation in DNA, malignant excitation of an infected tissue

What is ***GROUP 1*** of the carcinogenic effect? + example

Proven carcinogen, vinyl chloride

What is ***GROUP 2*** of the carcinogenic effect? + example

Expected carcinogen, DDT

What is ***GROUP 3*** of the carcinogenic effect? + example

Potential carcinogen, polyethylene

What is ***GROUP 4*** of the carcinogenic effect? + example

Non-carcinogen, caprolactam

HPC

highest permissable concentration

LC

lethal concentration

LD

lethal dose

NOAEL

no observable adverse effect

LOAEL

lowest observable adverse effect level