Pharmacological versus binding analysis of receptor systems: how do they interplay? Myometrial cell receptors for oxytocin as a paradigm.
Binding studies in various biological systems frequently indicate the presence of several binding sites for a biologically active ligand. They differ in their affinity for the ligand in question, binding capacity, and Hill coefficient, which suggests differences in the mechanisms of the binding site-ligand interactions. Identification of the 'true' receptors (sites initiating a cellular response) appears to be difficult. Three clusters of binding sites for oxytocin were found on rat myometrial cells. The oxytocin receptor seems to be linked to the medium-affinity site; the cooperation between the high- and medium-affinity sites in eliciting the uterotonic response seems likely, but lacks experimental proof. Dose-response analysis in partially irreversibly inhibited uterus preparations, the method of equipotent doses (Furchgott-Bursztyn method), and structure-activity analysis of oxytocin-like peptides acting as competitive inhibitors of oxytocin, turned out to be suitable for pharmacological analysis of this receptor system.
Pliska
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Department of Animal Science, Swiss Federal Institute of Technology, Zürich, Switzerland.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D005260:Female; D009215:Myometrium / Q000378:metabolism*; D051381:Rats; D011945:Receptors, Angiotensin / Q000378:metabolism*; D018045:Receptors, Oxytocin
D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin