Synthesis of intestinal basement membrane.

The rat small intestinal epithelial cell (enterocyte) has an average life span of 48h. Undifferentiated stem cells in the lower crypt region undergo division and differentiation into enterocytes as the cell moves on a basement membrane up the villus to reach the tip and be extruded into the lumen. The mechanism of this movement and relationship to basement membrane synthesis and/or renewal is unknown. This problem is discussed in regard to our findings suggesting that the major contribution to basement membrane synthesis and renewal may not be from the enterocyte.