Changes in the intestinal epithelial cells in abdominally irradiated germfree piglets

The renewal time of intestinal epithelial cells was established using tritiated thymidine in 14-day-old conventional piglets as 96 hours, but 192 hours in germfree piglets. In germfree piglets, irradiated by single abdominal exposure to 60Co gamma-rays with 3.87 x 10(-1) C kg (= 1500 R), the first degenerative signs in the ileal epithelial cells were found on the 13th postirradiation day. Since that day, the columnar epithelial cells exhibited progressive degeneration changes in their ultrastructure. Quickly growing, substituting flat epithelial cells occurred beginning with the 15th day after irradiation and covered parts of the leveled denudated intestinal mucosa. These flat epithelial cells also exhibited degenerative changes.