Influence of luminal pH on rat large bowel epithelial cell cycle.

The influence of luminal pH on the colonic epithelial cell cycle was studied by means of dietary modification to produce acidification of colonic contents. Forty male Sprague-Dawley rats were fed one of four diets: defined fiber free, fiber free diluted by either 100 g/kg lactulose or sorbitol, or 25 g/kg of MgSO4. After 2 wk, in vivo pH measurements were recorded at laparotomy under ether anesthesia in the cecum and proximal, mid-, and distal colon. Epithelial cells, isolated from these same regions, were measured for DNA content with flow cytometry in order to determine cell cycle stage. The pH values in all intestinal regions were highest with MgSO4 and then fiber free, sorbitol, and lactulose, the most acidic. In contrast, the percentage of cells in S phase (actively synthesizing DNA) was highest with lactulose and least with MgSO4. There was a significant inverse correlation between luminal pH and percent cells in S phase in the cecum (P less than 0.01), proximal colon (P less than 0.05), and distal colon (P less than 0.01). These results show that acidification of colonic contents by diet modification leads to increased epithelial cell proliferation.