Effect of simulated null gravity on the secretion of adrenomedullary hormones and miRNA-375 expression in rats / 解放军医学杂志

ABSTRACT

Objective To investigate the effects of simulated null gravity on the secretion of adrenomedullary hormones and miRNA-375 expression in rats. Method Fifty-six healthy adult male Wistar rats were randomly divided into 7 experimental groups (8 each), including suspension for 6h, 12h, 1d, 3d, 5d, 7d and 0h (control). Tail-suspension was used to establish the weightlessness animal model according to Morey-Holton's method. At the end of the experiment, the blood samples were obtained from the postorbitor vein, and the bilateral adrenal glands were harvested. The serum concentrations of catecholamines were determined by radioimmunological analysis. The expression of TH mRNA and miRNA-375 were assessed by quantitative RTPCR. TH protein in adrenal medulla was assayed using Western blotting analysis and immunohistochemistry. Results(1) The serum concentrations of rat's adrenomedullary hormones fluctuated obviously during the period of tail-suspension simulated weightlessness, with a temporary decline during 6-12h, followed by a sharp increase with a peak value on the 3rd day of suspension. (2) RT-PCR assay showed that TH mRNA expression in adrenal medulla of rats also fluctuated obviously, with a temporary decline at 6h and then elevated with a peak value at 1 day of suspension, followed by a downward trend forming a trough value on 5d of suspension. The immunohistochemistry showed that TH protein was stained as brown particles and the cytoplasm of adrenal medulla was stained deeply on 3d of suspension. (3) RT-PCR assay revealed that the expression of miRNA-375 in adrenal medulla increased temporarily at 6h of suspension, and it decreased significantly during 12h to 3d of suspension compared with that of control group (P<0.05). The miRNA-375 expression was up-regulated again during sustained suspension with a significant increase on 7d of experiment compared with that of control group (P<0.05). Conclusion The simulated weightlessness could affect the secretion of hormone of adrenal medulla in rats, and it may be related to the regulation of TH through miRNA-375 messenger network.