DNA synthesis in various cells of the exocrine part of the intact albino rat pancreas.

A differential count was made of the DNA-synthesizing cells in various parts of the exocrine epithelium of the intact pancreas of sexually mature male albino rats sacrificed 1 h after a single injection of thymidine-H3. The acinar cells showed low proliferative activity (0.18 plus or minus 0.05%). The highest labeling index was found in the epithelium of the ducts. However, the lining membrane of the ducts consisted of a heteromorphic system of cells with a varying level of DNA synthesis. The labeling index of the nuclei of the centroacinar cells was 2.5 times higher than that of the acinar epithelium and amounted to 0.48 plus or minus 0.17%, whereas the epithelium of the intercalary ducts had an extremely low labeling index: 0.09 plus or minus 0.09%, compared with 0.27 plus or minus 0.09% for the intralobular ducts and 0.50 plus or minus 0.08% for the interlobular ducts.