In pharmacology, why does EC50 not necessarily equal Kd?
I have the EC50 for nicotine stimulation of [3H]-
dopamine release, this value does not necessarily equal the Kd value for
nicotine at the receptor binding sites. Why?
- Simonizer1218Lv 72 months ago
If the relationship between receptor occupancy and response is linear, then the EC50 would equal the Kd, but it's a little more complex than that. Consider spare receptors for example. The EC50 may not represent binding to half of the total number of receptors, where in a binding assay, the Kd does involve all the receptors. I could go on with various other examples (partial agonists/antagonists, etc.), but hopefully this gives you some idea as to why these two measurements may not be equal.