Nucleic acid metabolism in proliferating and differentiating colonic cells of man and in neoplastic lesions of the colon.

Enzymes involved in the metabolism of nucleic acid precursors were assayed in proliferating and maturing cells in the colon of man and in cells removed from polypoid lesions of the colon. Cells were separated from superficial and deeper layers of colonie mucosa by a recently developed tissue-planing instrument. Gradients of thymidine kinase, thymidine phosphorylase, and adenine and hypoxanthine phosphoribosyltransferase activities were found to characterize different stages of cell differentiation in normal colon. Thymidine kinase and phosphorylase were highest in young, proliferating cells and decreased during differentiation and migration of the cells to the mucosal surface. Phosphoribosyltransferase activities were lowest in young, proliferating cells and increased during cell differentiation. In the polypoid lesions including carcinomas patterns of enzyme activity characterizing young, proliferative cells were found.