Drug receptor interactions 1 Flashcards
What is a receptor?
Specialised, localised proteins whose role it is to recognise stimulants and translate this event into an activation of the cell
Describe the interactions between drugs and receptors
Loose and freely reversible
Doesn’t include strong chemical bonds
When an agonist attaches to a receptor, what is formed?
An equilibrium
What are the 4 types of receptor?
- Enzymes
- Ion Channel
- Carrier molecules (transporters)
- Neurotransmitters, hormones, local hormone receptors
Where does a drug bind?
The active site of a receptor
What is an agonist?
Binds and causes a response
What is the law of mass action?
The rate of a chemical reaction is proportional to the product of the concentration of the reactants
[A] + [B] ⇌ [AB]
What is K1?
The rate constant for the formation of the complex (Drug-receptor)
What is K2?
The rate constant for dissociation
What equation using K1 and K2 gives a measure of affinity?
K1/K2
What is the rate of association as you add a drug?
K1 x [D] x [R]
What gives the rate of dissociation?
K2 x [DR]
Describe the features of high affinity binding
- Low concentration of drug needed in order to occupy the receptors
- High rate of association
How can you measure the affinity of a drug using an experiment?
- Using radio ligand binding, add a drug to the tissue
- Incubate until an equilibrium has been reached (forward rate = backwards rate)
- Filter: in the pellet: Radio ligand bound drug, in the solution: unbound drug
- Take the bound complex and add an excess of unlabelled drug
- This will displace the drug bound to the active site and any residual signal is from the non specific
- Subtract the non-specific from the total
What is equilibrium in terms of drug affinity?
Rate association= rate dissociation
