Loss of skeletal muscle mass happens under catabolic conditions of gravitational unloading because of combination proteolysis increase and synthesis decrease processes. Increase of proteolytic enzymes expression namely calpains and E3-ligases, MuRF-1 and MAFbx, was shown in soleus at short-time hindlimb unloading of rats. The aim of our study was analysis of protein synthesis elongation mechanism in rat soleus in conditions of different periods of hindlimb unloading. Male Wistar rats were divided into 4 groups: control group (C group, 221-225 g, n=10), hindlimb unloaded group during 3 days (3HS group, 226-240g, n=8), 7 days (7HS group, 223-232g, n=8) and 14 days (14HS group, 227-242g, n=8). Hindlimb unloading was carried out according to Ilyin-Novikov’s design with Morey-Holton’s modification. The experiment was conducted according to the rules of biomedical ethics (protocol No. 180 of April 6, 2011 was approved by the Russian Academy of Sciences Committee on Bioethics). The rats were sacrificed by nembutal overdose (75 mg/kg body wt), each soleus was weighted, immediately frozen in liquid nitrogen and stored at -80°C until analysis. Atrophy of soleus was found in all hindlimb unloaded groups, the most profound loss (by 40% vs. C group, p<0,05) of soleus mass was revealed after 14 days unloading. eEF2 is one of the important member of eEF family catalyzing simultaneous translocation tRNA and mRNA on a 80S ribosome. It’s known that eEF2 phosphorylation by its specific eEF2-kinase leads to prevention of elongation translation. We observed two-fold increase of eEF2k mRNA expression in rat soleus as early as 3 days unloading and it’s remained high till 14 days unloading as compared to control group (p<0,01). Moreover, eEF2k protein content was significantly greater than that in control (p<0,05) after unloading lasting 7 and 14 days. P-eEF2 level was also increased since 3 days unloading in comparison with the control group and remained so till 14 days unloading (p<0,05). It was shown significant decrease of eEF2 protein content after 7 and 14 days unloading relative to the control (p<0,05). However, it wasn’t found any changes in eEF2 mRNA level during all periods of unloading. Hereby, inhibition of eEF2 elongation factor function is a result of post-translational regulation by its eEF2-kinase which takes part in decrease of protein synthesis in soleus of rat after short- and long-term hindlimb unloading. The work was supported by grant RFBR 11-04-01769-a