Degradation of gastrin by gastric mucosal cells

Specific binding of radiolabeled gastrin by gastric mucosal cells prepared from guinea pigs was detected and examined. Specific cell binding of gastrin was found to be both pH and temperature dependent. Maximum binding of radiolabeled gastrin by gastric mucosal cells was demonstrated at pH 7.4 and at 4 degrees C. Substantial degradation of 125I-gastrin occurred during incubation with gastric mucosal cells. Gastrin degradation was detected both by loss of immunological reactivity with antibodies to gastrin and by abolition of subsequent specific binding after prior incubation with gastric mucosal cells. Degradation of gastrin was most marked with incubations conducted at pH 7.4 and at low pH (pH 2.0), suggesting the activities of at least two gastrin-degrading enzyme systems in the gastric mucosal cell preparation.