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±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 centroainar cells was 2.5 times higher than that of the acinar epithelium and amounted to 0.48±0.17%, whereas the epithelium of the intercalary ducts had an extremely low labeling index: 0.09±0.09%, compared with 0.27±0.09% for the intralobular ducts and 0.50±0.08% for the interlobular ducts.