Objective To establish a stable and reproducible animal model of abdominal intestinal firearm penetrating injury in a cold high-altitude environment.Methods Twenty landrace pigs were randomly and equally assigned to a low-altitude normal temperature(LN)group and a high-altitude cold(HC)group.The HC group was placed in a cold environment at high altitudes,and the LN group was placed in a normal-temperature environment at low altitudes.They were raised for 48 hours respectively.After anesthesia,they were suspended on the shooting range,and the right lower abdomen of the experimental pigs was shot with a gun.After injury,they were simply bandaged and transported back to the laboratory for observation in the normal temperature environment of the low altitudes.The vital signs and injuries at 0,2,4,8,12 and 24 h and 24 h survival rates of experimental pigs were compared.Laparotomy was immediately performed on the dead pigs and the experimental pigs still alive at 24 h to explore the injuries and observe the pathology of the small intestine and colon.Results The 24 h survival rate of the HC group was 70％,with no statistically significant difference compared to the LN group's 90％(P＞0.05).After the injury,the body temperature of both groups gradually increased.The body temperature of the HC group was significantly higher than the LN group at 0,2,4 and 8 h time points(P＜0.001),and the LN group exceeded the HC group at 24 h(P＜0.05).Both groups showed an initial increase followed by a decrease in heart rate,with the HC group significantly higher than the LN group only at 0 h(P＜0.01),and no statistically significant differences were observed at other time points(P＞0.05).Both groups showed an early increase and later decrease in respiratory rate,with the HC group higher than the LN group at 0,4,8,12 and 24 h(P＜0.05 or P＜0.001).There was no statistically significant difference(P＞0.05)between the HC group and the LN group in small intestine rupture,small intestine contusion,mesenteric injury,colon rupture and wound diameter.The pathology of the small intestine and colon in the HC group showed extensive necrosis and shedding of the mucosa layer,severe congestion and edema of the submucosa,and extensive lymphocyte infiltration.The LN group also showed similar symptoms but to a lesser extent.Conclusion This study established a pig model of abdominal firearm intestinal perforation injury in a cold environment at high-altitudes.The model has strong operability and stable damage,which can provide a reference for subsequent research.

Objective To observe the changes to,and possible mechanism of,intestinal permeability in pigs without direct injury after an abdominal-and intestinal-penetrating injury from firearms in cold environment at high altitudes.Methods Fifty-five experimental pigs were divided into two groups:high-altitude cold group(HC)and low-altitude normal temperature group(LN).According to the observation time,each group was divided into five experimental subgroups:0h,2h,4 h,8h,and 24 h.There were six pigs in each HC subgroup and five pigs in each LN subgroup.After euthanasia,intestinal tissues were taken,and the levels of the inflammatory factors TNF-α,and IL-6 in intestinal homogenate and the concentrations of intestinal permeability-related proteins DAO and D-lactate acid in blood were detected by ELISA method.The intestinal tissues of experimental pigs were taken at 0 h and 8 h for LN and 8 h for HC,and intestinal pathological changes were observed and scored after HE staining.The concentrations of Occludin,ZO-1,Claudin-3,TLR4,NF-κB,and MLCK(proteins related to intestinal permeability)were detected by Western blot to explore the effect of a cold environment at high altitude on secondary intestinal permeability changes after injury and the possible mechanisms.Results Both the HC group and LN group experienced typical abdominal intestinal penetrating injuries,and there were no significant differences in their abdominal infection scores or intestinal adhesion(P＞0.05).The levels of DAO and D-LA in the serum of experimental pigs in the HC and LN groups gradually increased over time.The levels of DAO and D-LA in the HC group were significantly higher than those in the LN group at all time points(P＜0.01 or P＜0.001).The fastest increase in DAO and D-LA in the HC group was 4 h to 8 h,while in the LN group,it was 8 h to 24 h.The pathological score of intestinal tissue in the HC group was significantly higher than that in the LN group of experimental pigs(P＜0.01).The inflammatory factors TNF-α and IL-6 both increased over time in the intestinal tissue of LN and HC groups.The most significant time point for a increase of inflammatory factors in the HC group was 4 h to 8 h,while in the LN group,it was 8 h to 24 h.The intestinal tissue IL-6 and TNF-α levels of experimental pigs in the HC group were higher than those in the LN group the entire time(P＜0.05,P＜0.01,or P＜0.001).The levels of occludin and ZO-1 in the HC group at 8 h decreased significantly compared to those of the LN group at the 8 h time point(P＜0.05),while claudin-3 showed a significant decrease in LN(P＜0.001).In the HC group,TLR4,NF-κB,and MLCK were both higher than those in the LN group at 8 h,and the difference was statistically significant(P＜0.05).Conclusions A high-altitude cold environment can lead to a secondary increase in intestinal permeability after abdominal-penetrating firearm injury,and its mechanism may be related to the TLR4/NF-κB/MLCK pathway.