Fetal rat pancreases, Day 16 through Day 22 postcoitum, were analyzed biochemically for amylase and chymotrypsinogen to assess acinar cell development in vivo. The interval between -eighteen and twenty days proved to be a critical period in the differentiation of the acinar component. Eighty- and thirtyfold increases in, respectively, amylase and chymotrypsinogen concentration were accompanied by a large increase in the acinar cell percentage of the pancreas.
Explantation of pancreas either before or after this critical period resulted in a developmental pattern which varied from that observed in vivo. The present organ culture system neither supported the differentiated acinar cell nor favored the further development of new acinar cells.
Using the present organ culture system, explants can be produced which are devoid of acinar cells and their exocrine enzymes.
