Receptor binding assay in vitro

Because the chemical structure of a molecule encodes its biological properties, structure has long served as the primary variable and determinant for the discovery of new drugs by medicinal chemists. For this reason, systematic structural modification has been the primary tool of choice to isolate and enhance a desired biologic activity. Moreover, with the relatively recent development of in vitro receptor-binding assays, combinatorial methods of chemical synthesis, and computer graphics, the overall approach to structural modification has become increasingly sophisticated. 

Figure 12.1 Examples of in vitro binding assays correlating with ADRs. Marketed drugs with known ADR profiles were tested in three different in vitro receptor binding assays and their IC50S (concentration required to achieve 50% inhibition) were determined. The percentage of drugs having (black bars) and not having (dotted bars) the stated ADR is...

The Hill equation has only limited applicability as a model to predict the expression of agonism, because the parameters from this empirical equation depend on both drug-specific and system-related properties, complicating the extrapolation and prediction from in vitro to in vivo systems. With a fully mechanistic model, Zuideveld was better able to predict the in vivo affinity and efficacy of 5-HTia receptor agonists from in vitro receptor binding assay. 

Akahori Y, Nakai M, Yamasaki K, Takatsuki M, Shimohigashi Y, Ohtaki M (2008) Relationship between the results of in vitro receptor binding assay to human estrogen receptor alpha and in vivo uterotrophic assay comparative study with 65 selected chemicals. Toxicol In Vitro 22(1) 225-231... 

In vitro receptor binding assay oj I-DOrA TAlT. 

The in vitro receptor binding assays of T-DOTATATE and Lu-DOTATATE using rat brain cortex membrane showed comparable affinities in the nanomolar range, placing these products among the radiopeptides with high binding affinity for somatostatin expressive receptors. 

Numerous artifacts that can give rise to misleading or erroneous data can accompany the in vitro receptor binding assay, and some of the more prominent of these are discussed below. In most instances, careful attention to detail and an immediate suspicion of interassay variations will suffice to avoid the most frequently encountered of these effects. 

Animal Species/Model Selection. Safety evaluation should include the use of relevant species, in which the test article is pharmacologically active due, for example, to the expression of the appropriate receptor molecule. These can be screened with in vitro rector binding assays. Safety evaluation should normally include two appropriate species, if possible and/or feasible. The potential utility of gene knockout and/or transgenic animals in safety assessment is discussed. 

Wang, J.-X., Yamamura, H. I., Wang, W, Roeske, W. R. The use of the filtration technique in in vitro radioligand binding assays for membrane-bound and solubilized receptors, in Receptor-Ligand Interactions. A Practical Approach, ed. Hulme, E. C., IRL Press, Oxford,... 

Methylscopolamine is a QTA obtained by N-methylation of scopolamine (Fig. 1). It exhibits non-selective antimuscarinic activity and is used as adjunctive therapy for the treatment of peptic ulcer, to treat nausea and vomiting due to motion sickness and for the management of irritable bowel syndrome [75], The tritiated form of methylscopolamine is often used in in vitro MR binding assays to investigate receptor affinity and competition by other agents [76],... 

Lung compliance in vivo Ciliary beat assays in vitro Mucus level assays in vitro Alveolar Type II cell surfactant secretion assay in vitro Pharmacological profiling — binding or functional assays at receptors, enzymes, ion channels, transporters... 

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