Mucosal gastrin receptor. II. Physical characteristics of binding.

Gastrin binding to rat gastric mucosal membrane preparations revealed a linear Scatchard plot, suggesting the existence of a single class of binding sites. Further studies revealed the absence of a positive cooperative effect. Because the system appeared to satisfy the conditions for Michaelis-Menten type kinetics, the determination of a Kd of approximately 3.6 X 10(-10) M was justified. These studies also demonstrated the efficacy of the specific activity of our iodinated gastrin. Trypsin treatment abolished specific binding of gastrin to the membrane preparation, indicating the protein nature of the receptor. The importance of maintaining extremely low temperatures during the incubation and wash period is demonstrated by the decrease in both the rate and the amount of dissociation at 0 degrees C compared with 30 degrees C.