what is the difference in osmolality between cytop
roughly equal between the two fluids
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what are the 2 main events that allow us to determ
1) affinity - how well the ligand binds to the receptor
2) efficacy - how well the binding causes a response
agonists has affinity to bind to receptor and has intrinsic efficacy
antagonist has affinity for the receptor but lacks intrinsic efficacy, presence of an antagonist makes it more difficult/impossible for agonist to work
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how can drug affinity be determined?
radioligand binding with saturation experiment
graph relationship between proportion of receptors and ligand concentration until maximum saturation is reached
method tells us about the affinity but not the efficacy
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how can a drugs efficacy be measured
put piece of tissue in a system to keep it healthy and measure a particular physiological property of the tissue
e.g. measure contraction increase with increase in ligand conc, then make a graph of log conc to response curve, measure max response and EC50 value ( effective conc of drug that causes 50% of response), allows us to determine the potency
low occupancy can produce maximum response e.g. Ach only needs to occupy 2% in lungs to cause maximu bronchioconstriction, receptor reserve system
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