模拟失重对大鼠血清胃泌素、胃动素和胃窦Cajal间质细胞的影响

目的：研究尾悬吊模拟失重环境对大鼠血清胃泌素（GAS）、胃动素（MTL）和胃窦Cajal间质细胞（ICC）的影响。方法：健康雄性Wistar大鼠64只随机分为8组（rt=8），按模拟失重时相分别设为6h、12h、1d、2d、3d、5d、7d和0h（地面对照组）组，采用尾悬吊法建立模拟失重动物模型。应用放免法测定血清GAS、MTL浓度，免疫组化和RT—PCR技术检测各组大鼠胃窦组织中c—kit蛋白和mRNA表达情况。结果：尾悬吊6、12h阶段，血清GAS浓度明显升高，与对照组比较差异有统计学意义（P〈0．05）；随尾悬吊时相延长，血清GAS含量呈逐渐下降趋势，与正常对照组水平相近。尾悬吊各组大鼠血清MTL浓度均升高，12h以后各组MTL浓度值与对照组比较，差异有统计学意义（P〈0．05）。免疫组化结果显示，c—kit蛋白阳性表达为棕褐色，主要分布在ICC胞体和突起，正常对照组大鼠胃窦肌层ICC（ICC—MY）呈连续性浓染，肌层内ICC（ICC—IM）亦明晰可见；6h-5d的尾悬吊过程中，大鼠胃窦ICC—MY连续性出现中断现象且逐渐明显，染色逐渐减弱，ICC—IM染色减弱的同时c—kit阳性ICC也明显减少；7d组胃窦组织中c—kit蛋白表达有所恢复。模拟失重各组及对照组大鼠胃窦组织中均有c—kitmRNA表达，尾悬吊6、12h组的c—kitmRNA表达明显下降，与对照组比较，差异有统计学意义（P〈0．05），1～3d组逐渐恢复，5d组又出现明显下降（P〈0．05），7d组c—kitmRNA表达值明显复升。结论：尾悬吊模拟失重对大鼠血清GAS、MTL和胃窦Cajal间质细胞c—kit蛋白及mRNA表达造成明显影响，可能导致胃动力障碍。

Simulated Weightlessness Affects the Serum Gastrin, Motilin, and In- terstitial Cells of Cajal in Rat Gastric Antrum

Objective： To investigate the effects of simulated weightlessness on serum gastrin, motilin and inter-stitial cells of Cajal（ICC） in rat gastric antrum. Methods： Sixty four adult male Wistar rats were randomly divid-ed into 8 experimental groups（n=8） including suspension for 6 h, 12 h, 1 d, 2 d, 3 d, 5 d, 7 d and 0 h（con- trol）. Tail-suspension was used to simulate the weightlessness animal model. Serum concentrations of gastrin and motilin were determined by radioimmunoassay. The c-kit protein and mRNA in rat gastric antrum were detected by immunohistochemical assay and RT-PCR technique. Results： Compared with the control group, the level of se- rum gastrin increased significantly in the early phase of tail-suspension with a peak value at 6 and 12 h（P〈 0.05） followed by declination and trend to normal range during the sustained suspension, and the level of serum motilin obviously increased in each groups except 6 h group（P〈0.05）. The immunohistochemistry assay showed that c-kit protein was stained as brown particles and mainly located in cell soma and dentrites of ICC. The myen- teric plexus ICC（ICC-MY） and intra-muscular ICC（ICC-IM） were deeply stained normally in rat gastric antrum. The expression of c-kit protein was obviously weakened during the period of 6 h to 5 d tail suspension, and the continuity of ICC-MY was gradually interrupted. However, the expression of c-kit protein was up-regulated in 7 d group. The semi-quantitative RT-PCR showed that the c-kit mRNA in rat gastric antrum was significantly down-regulated at 6 and 12 h of suspension compared with the control group（P〈0.05）, followed by a gradually re-covery at 1-3 d of suspension, then the c-kit mRNA was again significantly down-regulated at 5 d of suspension （P〈0.05）. Interestingly, the expression of c-kit mRNA was markedly increased at 7 d of tai-suspension. Conclu- sion： This study showed that the simulated weightlessness by tail-suspension could disturb the serum gastrin and motilin levels and affect the c-kit expression both at protein and mRNA levels in rat gastric antrum, and thus the gastric motility may be impaired.