[Exocrine enzymes in the pancreatic rudiments of the chick embryo developing in association with homologous or heterologous mesenchyme].

The aim of the present study was to investigate the development of enzymes in the chick pancreas and to study the influence of a heterologous mesenchyme (lung mesenchyme) on the differentiation of these enzymes. 1. The normal development of chymotrypsin, carboxypeptidase A, amylase, and lipase in the chick pancreas has been studied. The proteolytic activities as well as the amylase become detectable between day 14 and day 17. The total and specific activities of these enzymes remain rather low during about a week, and they show a spectacular rise just before hatching. In contrast to the proteolytic and amylolytic enzymes, lipase could not be detected before day 20 and showed a rapid increase just before and during hatching. 2. These enzymes have also been studied in the spleen and in the lung. Both organs show low and constant activities of chymotrypsin, carboxypeptidase A, and amylase. They are devoid of lipase. The latter enzyme appears to be strictly specific for the pancreas. 3. The specific activities of the various enzymes were measured in the various lobes of the pancreas; however, no significant differences were found. 4. All enzymatic activities were found in the organs obtained from an association of pancreatic epithelium with pulmonary mesenchyme and which developed in coelomic grafts. These activities were as high as in control organs where the pancreatic epithelium was not dissociated from its own mesenchyme. In conclusion it was found that the determined pancreatic epithelium, if it is associated with a pulmonary mesenchyme at the early embryonic stage, gives rise to biochemically normal exocrine pancreatic tissue.