| Background and Objective: China’s space programme has made a great progress inrencent years, and space medical researchers face many new challenges to ensureastronauts training and space activities. The studies have showed that agravity orsimulated weightlessness adversely affects the respiratory system, cardiovascularsystem, endocrine system, immune system, and genital system, etc. Understanding ofthe effects induced by the weightlessness on stomach is of great significance, while theliterature in this field was limited. This study aimed to investigate the effects ofsimulated weightlessness on the ultrastructure and oxidative stress in gastric mucosa ofrats, and try to provide a theoretical basis for the aerospace medical security.Methods：PartⅠ (1) Sixty-four adult male Wistar rats were randomly divided into8groups (n=8), including suspended for6h,12h,1d,2d,3d,5d,7d and0h (control).Tail-suspension was used to establish the animal model of simulated weightlessness.(2)At the end of the experiment, animals were anesthetized with chloral hydrate (300mg/kg) and blood samples from the inferior vena cava were acquired in each group, andgastric mucosa taken from glandular stomach area were divided into two parts: one forcryopreservation in liquid nitrogen tank, the other was conserved in4%paraformaldehyde (pH7.4) respectively.(3) GAS level in serum was determined byradioimmunoassay technique.(4) Hsp70and its mRNA in gastric mucosa were detectedby immunohistochemistry and RT-PCR technique respectively. PartⅡ (1) Eighty-eightadult male Wistar rats were randomly divided into11groups (n=8), includingsuspended for6h,12h,1d,2d,3d,5d,1wk,2wk,3wk,4wk and0h (control). Tail-suspension was used to establish the animal model of simulated weightlessness.(2)The animals were sacrificed after the experiment, and blood samples from the inferiorvena cava were acquired in each group, and gastric mucosa taken from glandularstomach area were divided into three parts: one for cryopreservation in liquid nitrogentank, the other two were conserved in4%glutaraldehyde and4%paraformaldehyde (pH7.4) respectively.(3) The ultrastructure of rat gastric mucosa was observed viaJEM-1230transmission electron microscope.(4) Contents of SOD, MDA and NO ingastric mucosa were detected by colorimetry technique and nitrate reductase testrespectively.(5) NOS2and COX2in gastric mucosa were assayed by usingimmunohistochemistry technique.Results:(1) Compared to the control group, the serum GAS significantly increased inanimals suspended for6h and12h (P<0.05), and then gradually decreased to normalranges in the late phase of the tail suspension (12h-7d).(2) The immunehisto-chemistry assay showed that the nuclei of gastric mucosal cells were deeply stained inthe early stage of suspension, followed by the stain of the cytoplasm of gastric mucosacells. The semi-quantitative PCR showed that the Hsp70mRNA in gastric mucosa wasalso significantly up-regulated at the early phase of suspension compared with thecontrol group (P<0.05).(3) The transmission electron microscope revealedultrastructural changes in part of gastric mucosa cells including condensation ofchromatin around the perinuclear membrane, mitochondrial swelling, dilatation of theendoplasmic reticulum and vacuolar degeneration under simulated weightlessness, withmarked alteration during2wk to4wk suspension versus control group.(4) The contentof SOD, MDA and NO in rat gastric mucosa were raised rapidly in the early stage ofsuspension, followed by a decline, and increased again in the late phase of suspension.(5) The immunohistochemistry showed that both of NOS2and COX2were deeplystained in the cytoplasm of gastric mucosa cells in the early hours of suspension (6h to 2d), then weakened obviously in3d to5d tail-suspended rats, and dark stained againin2wk to4wk suspended rats compared with normal controls (P<0.05).Conclusions: The simulated weightlessness by tail suspension acts as a kind of stresswhich could induce fluctuation of the serum GAS level and changes of Hsp70expression in the gastric mucosa at both protein and mRNA levels, and abnormality ofNOS2and COX2proteins were also founded, accompanied by ultrastructural alterationin the gastric mucosa. The results suggested that (1) the simulated weightlessness maylead to acute gastric mucosal lesion;(2) GAS and Hsp70along with NOS2/COX2mayplay important roles in gastric stress response and adaptation to simulatedweightlessness. |
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