Transport of amylase across the apical membrane of the pancreatic exocrine cells. Quantitative analysis of zymogen granules.

The number or the size of the zymogen granules was calculated in a determined volume slice of pigeon pancreas and in a total cellular fraction of zymogen granules isolated from a part of this organ having the same volume. The obtained values were not significantly different. These results are discussed in relation to the mechanism of digestive enzyme secretion. They confirm that amylase can be transported molecule by molecule across the intact apical membrane of the pancreatic exocrine cells.