The quantitative aspects of drug receptor interactions

The determination of the affinity of a partial agonist to the β receptor by its capacity to activate adenylate cyclase is difficult because of the low activities induced by these compounds. In many cases, the partial agonists also possess low affinity to the receptor, thus compounding the situation even more. The authors therefore developed a simple method to determine the affinity of partial agonists to the β receptor by measuring their capacity to interfere and compete with the activation by the full agonist (the hormone). This can be accomplished by determining a series of activation curves by the full agonist measured in the presence of different concentrations of the partial agonist. This method is general and based on simple rules of enzyme kinetics.