Intestinal morphology and cell production rate in aging rats.

Age-related changes in the gut were investigated in male gnotobiotic rats, living in a controlled and constant environment until death. Parameters of the regenerative compartment of the jejunum and ileum were the cell production rate (measured by a stathmokinetic technique), the number of crypts, and the crypt:villus ratio. Parameters of the functional compartment were the average surface area of the villi, height and broadness of villi, etc. Age did not change the size of individual villi or crypts or the cell production rate. The number of crypts and, to the same extent, the number of villi increased with age, indicating a continuation of mucosal growth up to an age of 2 yr.