Aspartic proteinases in gastric mucosa of the rat: absence of pepsinogen I, genetic polymorphism of pepsinogen II, and presence of slow-moving proteinase.

We have examined relationships among the aspartic proteinases in rat and human gastric mucosa by electrophoretic analysis in polyacrylamide gel and by immunoblotting and immunohistochemical staining using rabbit antisera to human pepsinogen I (PG I), pepsinogen II (PG II), and slow-moving proteinase. By electrophoretic analysis, the major proteolytic bands in mucosal extracts from each of three strains of rats had rates of anodal migration that were similar to the fastest migrating isozymogens of human PG I. However, immunoblots revealed that these bands and several minor proteolytic bands with slower rates of anodal migration reacted with antiserum to PG II. Two proteolytic bands in rat gastric mucosa that migrated concurrently with human slow-moving proteinase reacted with antihuman slow-moving proteinase reacted with antihuman slow-moving proteinase. None of the proteolytic bands in rat gastric mucosa reacted with anti-PG I. By immunohistochemical staining, anti-PG I failed to stain any cells in rat fundic gland or antral mucosa. By contrast, anti-PG II stained mucus neck and chief cells in fundic gland mucosa and pyloric gland cells in antral mucosa, and anti-slow-moving proteinase stained surface and foveolar epithelial cells throughout the stomach. The results indicate that the gastric mucosa of the rat does not contain PG I.