CELL PROLIFERATION KINETICS IN THE GASTROINTESTINAL TRACT OF MAN. I. CELL RENEWAL IN COLON AND RECTUM*

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Abstract
In order to begin a comparison of cell renewal in different parts of the human gastrointestinal tract and to evaluate possible relationships between cell renewal and disease states, estimates were made of the mean proliferative time and the phases of the proliferative cycle of the colonic and rectal epithelial cells. The rate of reduction of label in individual cells and the rate of removal of cells from the mucosa were also measured. After injection of H3-thymidine, the mean proliferative time of epithelial cells of colon and rectum was found to be about 1 day, divided into a phase of DNA synthesis lasting 11 to 15 hours, a post-synthetic, premitotic phase that combined with mitosis, lasts 1 to 2 hours, and a postmitotic, presynthetic phase of 10 to 30 hours. About 15% of the crypt cells are in the synthesis phase. Cell renewal proceeds at a mean rate of 1.2 cells per 100 cells per hour, and the entire colonic and rectal crypts are replaced in about 3 to 4 days. Labeled cells migrate at a rate of about 0.9 cell positions per hour. The area of cell proliferation occupies about 65% of the colonic and rectal crypt columns.