Binding characteristics of pancreatic polypeptide receptors on rat hepatic membranes.

Aim: To study the binding characteristics of pancreatic polypeptide (PP) receptors on rat hepatic membranes.
Methods: 125I-PP suitable to study interaction between ligand and receptors were prepared. 125I-porcine PP and 125I-duck PP were used to study PP receptor binding in the controlled conditions.
Results: The binding of 125I-porcine PP to receptors on rat hepatic membranes was time- and temperature-dependent. The specific binding of 125I-porcine PP was inhibited by unlabeled porcine PP in a concentration-dependent manner, whereas duck PP was only partially inhibited in the high concentration (> 500 nmol.L-1). Scatchard analysis produced a curvilinear plot, suggesting multiple affinity binding sites, i.e., high-affinity and low-affinity with dissociation constants (Kd) 5.4 and 158 nmol.L-1, respectively.
Conclusion: Rat hepatic membranes possessed specific PP receptors and porcine PP binding activity was much higher than that of duck PP.