[An experimental study on the apoptosis of rabbit small intestinal cells during early postburn stage]

To explore the significance of apoptosis of rabbit small intestinal mucosal epithelial cells and lymphocytes, and lymphocytes of lumbrical process at early postburn stage.

Twenty-five Japanese white rabbits were randomly divided into 5 groups with 5 in each group, i.e. normal control (N), 3-postburn-hour group (3 PBH), 6 PBH, 12 PBH and 24 PBH groups. The rabbits in all PBH groups were inflicted with 30% TBSA III degree of flame burn on the back. The intestinal tissue samples were harvested from 5 anatomical sites for HE staining, electron microscopic examination and the detection of apoptosis in situ by TUNEL method at all the postburn time points. The results of TUNEL slides were analyzed statistically.

HE staining revealed that there were relatively abundant apoptotic cells scattering solitarily in the lymph nodules and diffuse lymphatic tissue in the mucosal epithelial and mucosal lamina propria (and partially extended into the submucosal layer) of the intestine and lumbrical process in all burn groups. There were some disruption of intestinal mucosa in 24 PBH group. But no obvious inflammatory reaction and signs of necrosis were observed in all the slides. Apoptotic body formation could be identified by EM. Large number of blue-black positive cellular nuclei were revealed by TUNEL method with their distribution as similar to that found by HE staining. When comparing with those in control group, the apoptotic cells in small intestine and lumbrical process were increased obviously (P < 0.01) in 3 PBH group and reached the top level in 6 and 12 PBH groups (P < 0.01), declining thereafter to near value of 3 PBH in 24 PBH group, though it was still higher than control (P < 0.05). The number of apoptotic epithelial cells in middle distal portions of small intestinal mucosa in burn groups was much higher than that in proximal intestine (P < 0.05).

There was a large number of apoptotic cells in rabbit small intestinal mucosal epithelium, gut associated lymphoid tissue and lymphocytes in the lumbrical process, especially in the middle and distal portions of the intestine. These change might be the cellular basis of postburn intestinal translocation of bacteria and endotoxin.