Pancreatic Zymogen Granules Differ Markedly in Protein Composition

The activities of both chymotrypsin and amylase in individual zymogen granules of rat pancreas were measured by means of micromanipulation and microfluorometric methods. The enzyme content and the ratio of amylase to chymotrypsin varied widely among granules taken from the same animal. These results are compatible with short-term nonparallel bulk secretion of the two enzymes through exocytosis. The distribution of each enzyme activity in a population of granules suggests quantal packaging of amylase and chymotrypsinogen into the granules.