Pancreatic centroacinar cells. The regulator of both exocrine and endocrine function.

The relationship between pancreatic centroacinar cells (CAC), the acinar cells, and the endocrine cells was examined in fetuses and newborn Syrian hamsters histologically, immunohistochemically, and electron microscopically. Pancreatic anlage, composed of undifferentiated cells and a few alpha cells, were found at day 12, delta cells at day 13, acinar cells at day 14, and beta cells at day 15 of the gestation. Intermediate cells (hybrid cells with both zymogen and endocrine granules) were also found after day 14. In the late-gestational period and after birth, two types of acini could be distinguished: one was composed exclusively of acinar cells and the second of acinar and CAC. In the latter type, some CAC covered the surface, lateral, and basal portion of the acinar cells, which showed a relative reduction of zymogens and increased autophagic vacuoles, a finding that indicated that CAC control the zymogen release from the acinar cells. Two types of CAC were encountered: dark cells with cytoplasmic processes located on the surface of acinar cells and larger light cells located between the acinar cells. The transitional forms between the light CAC and endocrine cells were found frequently at day 15 and a day after birth. During the endocrine cell differentiation, the committed cells lost their connection to the lumen by the force of the cytoplasmic processes of the dark CAC, which then overlaid the differentiated endocrine cells. From these findings, it can be concluded that CAC control both the pancreatic exocrine secretion and endocrine cell function.