A simple method for determining epithelial cell turnover in small intestine. Studies in young and aging rat gut.

Epithelial cell migration in animal gut classically is measured by autoradiography after systemic administration of tritiated thymidine. A migration rate is calculated from observations of the leading edge of villus epithelial cells containing labeled nuclei at varying time periods after tritiated thymidine injection. This method is very accurate, but laborious, time consuming, and costly. A new, simplified method for measuring epithelial cell measurement of [3H] deoxyribonucleic acid specific activity in frozen sections of intestine cryostat-cut from villus tip to crypt base. The leading edge of [3H]deoxyribonucleic acid can be detected reproducibly (coefficient of variation 11.25%). Autoradiographic and chemical methods for determining the leading edge of labeled cells compared favorable (r=0.848). Epithelial cell migration rates in barrier-reared Fisher 344 aging (27 mo) and young control (4-5 mo) rats were compared and no differences were detected in duodenum, jejunum, or ileum. Labeled epithelial cells reached the villus tip sooner in the ileum than in duodenum or jejunum. However, crypt-villus column heights were greater in duodenum and jejunum and the calculated epithelial cell migration rate was faster in upper intestine than in the ileum. Although ileal epithelial cells are shed from the villus sooner than cells in the upper intestine, the rate of cell migration in ileum is slower.