CONTROL OF INTESTINAL EPITHELIAL REPLACEMENT: LACK OF EVIDENCE FOR A TISSUE-SPECIFIC BLOOD-BORNE FACTOR

The small intestine of rats was cut across in two places, about 14 and 50% of the length of the small intestine from the pylorus, and continuity was re-established by suturing the proximal and distal ends. The resulting sac of small intestine, averaging 36% of the total length of the small intestine, had its upper end closed off, and its lower end anastomosed, either to the intestine-in-continuity (an ‘intestine-sac’), or to the skin of the abdominal wall (a ‘skin-sac’). On the ninth post-operative day, the cell production rate in squashes of micro-dissected whole crypts of Lieberkühn was measured by mitotic blockade with Colcemid. The rate of cell production in unoperated and sham-operated rats was 30 cells/crypt/hr, throughout the length of the small intestine. In the intestine in continuity, the rate increased to an average of 46 cells/crypt/hr above the anastomosis, and to 54 cells/crypt/hr below it. At the lower end of the ‘intestine-sac’, which drained into the intestine-in-continuity, the rate was 39 cells/crypt/hr, while in the lower end of the sac which drained to skin the rate of cell production was only 16 cells/crypt/hr. This significantly lower cell production rate in intestine which was not in contact with ingesta is taken to be evidence of the importance of local, rather than blood-borne factors in the control of epithelial replacement.