重度烧伤鼠肠上皮细胞及其刷状缘谷氨酰胺转运的变化

Alterations of glutamine transport in intestinal epithelial cells and brush border membrane in rats after severe burn injury

目的探讨烧伤后肠上皮细胞及其刷状缘谷氨酰胺（glutamine,Gln）转运变化规律。方法将40只Sprague-Dawley大鼠随机分为正常对照组（8只）、烧伤组（烧伤后1、3、5、7 d,每个时相点8只）。正常对照组只麻醉和剃毛,不予烧伤;烧伤组给予90℃水烫伤18 s,造成30%体表面积Ⅲ度烧伤。2组给予正常饮食及饮水。联合应用胶原酶Ⅸ和中性蛋白酶Ⅰ消化法提取大鼠小肠上皮细胞（intestinal epithelial cells,IEC）,采用Mg^2＋差速离心法制备大鼠小肠刷状缘膜囊泡（brush border membrane vesicles,BBMV）,检测进入BBMV及IEC中的[^3H]-Gln的放射性强度,观察伤前及烧伤后1、3、5、7 d大鼠肠道BBMV及IEC中Gln转运速率的变化。结果采用Mg^2＋差速离心法成功提取大鼠肠上皮BBMV。发现肠上皮细胞中Na＋依赖性Gln转运主要依靠BBMV,大约占总量的60%;烧伤第1天BBMV中Gln转运效率明显下降（P〈0.05,P〈0.01）,伤后3-7 d有所增高,但差异无统计学意义（P〉0.05）。IEC中Na^＋依赖性Gln转运变化不明显,而非Na＋依赖性Gln转运则有逐步增高的趋势,在伤后7 d明显高于对照组（P〈0.05）。结论肠上皮细胞对Gln的转运主要依靠BBMV中Na^＋依赖性转运,烧伤后BBMV转运Gln的能力先降低后增高,而IEC对非Na＋依赖性Gln转运则呈逐步增高的趋势。

Objective To investigate the change of glutamine（ Gln） transport in intestinal epithelial cells（ IEC） and brush border membrane vesicles（ BBMV） in rats after burn injury. Methods Forty Sprague-Dawley rats were randomly divided into normal control（ C） group and burn injury（ B） group. The rats in the C group only received anaesthesia and shaving. The rats in the B group were inflicted with 30%body surface area of full thickness burn by soaking in 90 ℃ water for 18 s. IEC was separated by digestion with collagenase Ⅸ and dispaseⅠ,and BBMV was prepared by magnesium precipitation. The transport rate of[^3H]-Gln into BBMV and IEC was quantitatively detected by radioactivity count per minute（ CPM） assay to observe the change of Gln transport rate before burn and on postburn day（ PBD） 1,PBD3,PBD5 and PBD7.Results BBMV was successfully extracted from the rats by magnesium ion differential centrifugation. It was discovered that Na^＋-dependent Gln transport in IEC mainly relied on the BBMV,accounting for about 60% of the total. Compared with the C group,the Gln transport rate in BBMV was slightly increased in the B group（ P〈0. 05） after burn injury except remarkable decrease on PBD1（ P〈0. 01,P〈0. 05）. The change of Na^＋-dependent Gln transport in IEC was not significant（ P〉0. 05）,but Na^＋-independent Gln transport in IEC showed a rising trend and significantly increased on PBD7（ P〈0. 05）. Conclusion Gln transport in intestinal epithelial cells rely mainly on Na^＋ dependent transport in BBMV. The overall trend of Gln transport in BBMV is firstly decreased and then increased after burn,while that in IEC shows a gradually increasing trend.