Mucosal gastrin receptor. III. Regulation by gastrin.

Specific binding of 125I-labeled gastrin to rat gastric mucosal membranes was found to vary with serum gastrin levels. The dissociation equilibrium constants were not significantly different between receptor preparations. However, the binding capacities of the membrane preparations were directly correlated with serum gastrin levels. Fasting, feeding a liquid diet, and antrectomy significantly decreased serum gastrin and the concentrations of the gastrin receptor. Treatment of fasted and liquid-fed animals with pentagastrin prevented the decrease in receptors. Vagotomy increased both binding capacity and serum gastrin levels. These data indicate that gastrin stimulates the production of its own receptor. The upregulation of the gastrin receptor was evident if the binding capacity was expressed per milligram of protein, per microgram of DNA, or per amount of 125I-labeled choleragen bound to the same membrane preparation. This indicates that the biological response to gastrin is controlled in part by the regulation of the number of gastrin receptors present and that gastrin plays a role in this regulatory process.