Long-term organ culture of embryonic rat pancreas in a chemically defined medium.

Embryonic rat pancreas anlagen have been grown in a chemically defined medium, subdivided biweekly and recultured for a total time of 10 weeks. The total mass increment during this time was in excess of 1000-fold. Samples were removed for light and electron microscope examination and for periodic measurement of enzymatic activity. Morphogenesis and cytodifferentiation occurred, peripheral outgrowth of epithelial buds was followed by the formation of interconnecting tubular structures and, eventually, by the appearance of distinctive acinar cells with zymogen granules. Mitotic figures became conspicuous at the periphery of explants within a day after each subdivision resulting in the formation of new tubular structures and acini. In general, the central area of the explants presented more mature acini with zymogen granules than was manifested at the periphery. The enzymatic activities of amylase, lipase, and chymotrypsin developed maximally during the first week of culture, reached a plateau level by the second week, and remained at a relatively constant level throughout the 10-week culture period.