OBJECTIVETo explore influence of oxidative stress reaction on apoptosis rate and expression of apoptosis-related genes bax and bcl-2 of enterocytes in severely burned rats with delayed resuscitation on the plateau.

METHODSOne hundred and twenty rats subjected to 30% TBSA full-thickness scald on the back were devided into plateau experimental group (PE, altitude 3840 m) and Lanzhou experimental group (LE, altitude 1517 m). Then LE and PE groups were subdivided into Lanzhou immediate fluid resuscitation group (LIFR, with immediate intraperitoneal injection of isotonic saline after scald, 40 mL/kg), Lanzhou delayed fluid resuscitation group [LDFR, with intraperitoneal injection of isotonic saline at 6 post scald hour (PSH), 40 mL/kg], and plateau immediate fluid resuscitation group (PIFR, with immediate intraperitoneal injection of isotonic saline after scald, 40 mL/kg), plateau delayed fluid resuscitation group (PDFR, with intraperitoneal injection of isotonic saline at 6 PSH, 40 mL/kg). Another 12 rats were divided into Lanzhou sham scald group (LS) and plateau sham scald group (PS), with 6 rats in each group. Rats in LS and PS groups were sham scalded in a water bath for 15 s without fluid infusion. Rats were sacrificed at 6, 12, 24, 48, 72 PSH for collection of small intestine samples to determine the contents of malonaldehyde (MDA) and total hydrosulfide (TSH). The apoptosis of enterocytes was determined by TUNEL, and the expression of bax and bcl-2 in epithelial cells were observed by immunohistochemical method. Intestinal sample of LS and PS groups were collected to determine the contents of MDA and TSH.

RESULTSAfter being scalded, content of MDA in intestinal tissue of rats in LDFR group and PDFR group was respectively greater than that in LIFR group and PIFR group (P < 0.05 or P < 0.01). Intestinal tissue content of MDA of rats in LDFR group (9.8 +/- 4.0 nmol/mg) and PDFR group (10.2 +/- 1.3 nmol/mg) was respectively greater than that in LIFR group (9.5 +/- 2.7 nmol/mg) and PIFR group (9.6 +/- 1.1 nmol/mg) (P < 0.05) at 24 PSH. After being scalded, intestinal content of TSH of rats in PE group and PDFR group was respectively smaller than that in LE group and LIFR group (P < 0.05). A multitude of brown positive apoptotic cells were observed in PDFR at 6 and 12 PSH. Absorbance values in LDFR group, PIFR group, and PDFR group were higher than that in LIFR group at each time point (P < 0.05 or P < 0.01). A multitude of bax positive cells were observed in intestinal mucous membrane in PDFR at 6 and 12 PSH. Expression of bal-2 was negative in PE group, and LIFR and LDFR groups at 6, 12 PSH, and it was weakly positive in LIFR and LDFR groups at 24, 48, 72 PSH.

CONCLUSIONSEnhancement of bax expression and weakening of bcl-2 expression in enterocytes are induced by the severe oxidative stress reaction in intestinal mucous membrane after burn with delayed resuscitation on the plateau, which may be one of the important reasons in inducing an increase in apoptosis of enterocytes.