高原严重烧伤延迟复苏大鼠脑损伤与兴奋性氨基酸水平变化

Early changes of injured brain tissues and excitatory amino acids in severely burned rats after delayed fluid resuscitation at high altitude

目的:观察高原严重烧伤延迟复苏后早期大鼠脑损伤及兴奋性氨基酸含量的变化.方法:130只雄性Wistar大鼠随机分为烧伤即时复苏组(n=60)、烧伤延迟复苏组(n=50)和正常对照组(高原地区正常对照组n=10和兰州地区正常对照组n=10).前两组动物被制成高原(海拔3800m)烧伤实验动物模型(TBSA30%,Ⅲ度).运用高效毛细管电泳法检测脑组织中兴奋性氨基酸(谷氨酸,Glu)含量,采用干、湿重比重法测定脑组织含水量,原位末端标记(TUNEL)观察脑皮质神经细胞凋亡.结果:从兰州地区急进高原后,大鼠脑组织Glu含量、脑组织含水量、脑皮质中TUNEL阳性细胞数均未发生明显改变(P>0.05);高原严重烧伤后脑组织Glu水平于伤后1h即显著降低,持续至伤后24h,于伤后72h恢复至正常水平(P<0.05);延迟复苏组脑组织Glu水平在观察时限内均低于上述两正常对照组,延迟复苏组与即时复苏组相比除在伤后12h时相点无统计学差异外,其余时相点均低于即时复苏组(P<0.05).而脑组织含水量于伤后6h开始升高,于24h达高峰,于伤后7d降至正常水平;高原烧伤延复组变化趋势同高原烧伤即复组,但伤后7d仍未恢复.脑皮质TUNEL阳性细胞在伤后1h即增多,也于伤后24h达高峰,伤后7d仍高于正常水平.结论:由兰州地区急进到高原地区,并不足以导致大鼠脑组织中兴奋性氨基酸含量发生变化及大鼠脑水肿的发生和脑皮质凋亡细胞数的增加;高原严重烧伤及延迟复苏后,细胞外兴奋性氨基酸减少,同时伴有受伤大鼠迅速出现脑水肿,脑皮质凋亡细胞显著增加.

AIM： To explore the early changes of injured brain tissues and excitatory amino acids （EEA） in severely burned rats after delayed fluid resuscitation at high altitude. METHODS： Totally 130 male Wistar rats were randomly divided into 4 groups： delayed fluid resuscitation group （ HDFR, n = 50 ）, immediate fluid resuscitation group （ HIFR, n = 60 ） , normal control group at high altitude （HNC, n = 10） and normal control group （LNC, n = 10） in Lanzhou region （ 1517 m）. At 3800 m, the animals in the HDFR and HIFR groups were burned severely （TBSA 30% , Ⅲ degree）. At different time points （PB 1,6, 12, 24, 72 h and 7 d） after burn, the levels of the excitatory amino acids （ glutamic acid, Glu） in rats＇ brain were measured by high-performance capillary electrophoresis （HPCE）; brain water was determined through measuring the wet/dry weight ratio; the apoptotic cells in pallium were detected by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） assay. RESULTS： From Lanzhou region to high altitude rapidly, the levels of Glu, brain water content and TUNEL-positive cells in rats＇ brain had no obvious changes（ P 〉 0.05 ）. After severe burn at high altitude, the levels of Glu decreased at PBlh and kept on to PB24h, and returned to the normal level at PB72h （P 〈 0.05 ）. In HDFR group, the Glu levels remained lower than those in HNC and LNC groups; apart from PB12h, the Glu levels in HDFR group were obviously lower than those in HIFR group at each time point. Brain water content in HIFR group began to increase at PB6h, reached the maximum at PB24h, and decreased to the normal at PB7d; the tendency in HDFR group was the same with HIFR group except that it did not recover to the normal at PB7d. The apoptotic cells in pallium elevated at PBlh, peaked at PB24h and remained at a higher level at PB7d. CONCLUSION： Arriving at high altitude rapidly from Lanzhou region, that can not result in the changes in the levels of Glu, brain water and TUNEL-positive cells in rats＇ brain. The severe bum with delayed fluid resuscitation at high altitude can lead to the decrease of extracellular EAA accompanied with the appearance of cerebral edema and the augmentation of apoptotic cells in pallium.