Early proliferative events following intestinal resection in the rat.

Partial resection of the small intestine results in compensatory proliferation and adaptation in the remaining small intestinal mucosa. The molecular mechanisms governing the proliferative response are not known, nor has the timing of events associated with proliferation been adequately defined, particularly during the period just after resection. We designed experiments to characterize early (within 24 h) proliferative events associated with proximal intestinal resection and sought to determine the cell type that first responds to proliferative stimuli. Twenty-one day old male Sprague-Dawley rats underwent a 70% proximal intestinal resection or transection (control). Poly(A) RNA was isolated from the distal (ileal) remnants. Northern blots showed a marked induction of the immediate early genes zif-268, nup-475, and c-myc 1-3 h following resection, but not following transection. Immunohistochemical analysis of c-myc expression in ileal crypt epithelial cells showed a biphasic induction that was most marked 6 h after resection and less prominent 24 h after resection. Immunostaining with 5-bromodeoxyuridine (5-BrdU) was restricted to ileal crypt nuclei and was maximal 24 h after resection. All these events were observed in the absence of nutrient intake. Taken together, these data show that a potent nutrient-independent stimulus for intestinal epithelial cell proliferation occurs within minutes of partial small intestinal resection and that the first targets of this stimulus are crypt epithelial cells in the residual intestine.