Enhanced susceptibility of DNA-synthesizing nuclei of epithelial cells of the intestine to acid hydrolysis.

Albino mice were injected intraperitoneally with tritiated thymidine and killed 1/2 and 30 h later. Pieces of ileum were excised and fixed. Tissue sections were hydrolyzed with 5 N HCl at 21 degrees C for 1/2, 1, 2, 3, 4 and 6 h, some sections remained unhydrolyzed. Both the hydrolyzed and nonhydrolyzed sections were autoradiographed. Grain counts per labelled nucleus of either cryptal (DNA-synthesizing) or villous (DNA-nonsynthesizing) cells nonhydrolyzed and hydrolyzed for various time intervals were recorded. The results indicate, that the grain count of nonhydrolyzed, labelled nuclei from cryptal cells was by 1.49 higher than that of villous cells demonstrating the rate of grain counts diminution caused by cell divisions. Hydrolysis caused a diminution of grain count of cryptal cells by approximately 15% higher than that of the grain count of villous cells.