Purpose of the investigation was to determine the cytochrome c content and associated gene expression in cardiomyocytes and m. soleus fibers obtained from rats following 6, 12, 18, 24 and 72 hours of tail suspension. Cellular respiration was measured using Sax's polarography as a parameter reflecting the mitochondrial activity. In cardiomyocytes, cytochrome c in the protein membrane-mitochondrial fraction grew 34.6% (p < 0.05) after 18 hours of suspension relative the control. Cycs and gapdh expression was not altered, while parameters of the cardiomyocyte cellular respiration were increased. In m. soleus fibers, cytochrome c made a fall following 24-hr suspension. mRNA cycs was found reduced significantly after 6 hours and cellular respiration intensity declined reliably after 72 hours of gravitational unloading.