Bax is required for increased enterocyte apoptosis after massive small bowel resection.
BACKGROUND
Massive small bowel resection (SBR) increases rates of both enterocyte proliferation and apoptosis. Previous studies have demonstrated increased intestinal expression of proapoptotic bax mRNA and protein, as well as the appearance of an 18-kd bax cleavage product within 12 hours of SBR. This study tested the hypothesis that bax is required for postresection increases in enterocyte apoptosis.


METHODS
Male bax-null and C57Bl/6 (control) mice underwent either a 50% proximal SBR or sham operation. After 3 days, the remnant ileum was harvested and weighed. Apoptotic indexes, proliferation indexes, villus heights, and crypt depths were determined.


RESULTS
The usual adaptive increases in ileal wet weight, crypt depth, and rate of proliferation occurred in both the control and bax-null mice. Resection significantly increased the rate of apoptosis in the control mice; however, it failed to alter the apoptotic index in the bax-null mice.


CONCLUSIONS
Bax is necessary for the increase in apoptosis that occurs after SBR, but its absence has no significant effect on short-term adaptation. These findings suggest that enterocyte proliferation and apoptosis are differentially regulated during intestinal adaptation.
Division of Pediatric Surgery, Children's Hospital Medical Center, Department of Surgery, University of Cincinnati College of Medicine, OH 45229-3039, USA.
L E
LE
Stern
F
F
Huang
C J
CJ
Kemp
R A
RA
Falcone
C R
CR
Erwin
B W
BW
Warner
D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D020895:Enterocytes / Q000166:cytology / Q000473:pathology* / Q000502:physiology; D007082:Ileum; D007421:Intestine, Small / Q000601:surgery*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000235:genetics
C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor