RESUMO
Objective To study the effect of tail-suspending on myostatin(MSTN)expression in the soleus muscle of rats.Methods The MSTN mRNA levels in soleus muscle of tail-suspended and normal control rats were measured and compared.Results The MSTN mRNA in soleus muscle of tail-suspended rats was 2.2 times(hind limb unloading for 14 days)and 3.5 times(hind limb unloading for 30 days) higher than that in normal control rats (P<0.05).The relative wet weight of the soleus muscle in tail-suspended rats was decreased by 11%(unloading 14 days)and 1 9%(unloading 30 days),respectively,compared with that in normal control rats.Conclusion The expression of MSTN mRNA is elevated in the soleus muscle of tail-suspended rats,probably due to atrophy of the soleus muscle.
RESUMO
The aim of this study was to determine the adaptation of atrial natriuretic peptide(ANP) to simulated weightlessness. The level of immunoreactive plasma ANP level and the expression of right atrial ANP mRNA were assessed in male Sparague-Dawley rats during 2 weeks of head-down suspension(HDS) The rats were placed in a -45 degrees anti-orthostatic position. The plasma ANP level was investigated by radioimmunoassay and ANP mRNA was expressed by Northern blot analysis. The changes in daily water intake, body weight and arterial hematocrit did not show the statistical significances during HDS. The plasma ANP level slightly increased after 1 day of HDS, the response was transient and then decreased below the control levels. The expression of the ANP mRNA increased after 1 day, the peak value occurred at 3 days of HDS and thereafter ANP mRNA showed the similar patterns compared to the changes of plasma level. On the basis of these findings, we conclude that the initial adaptation of ANP to increased control blood volume in rats occurs between 3 and 7 days of HDS, and the ANP acts an important role during regulatory process to central hypervolemia at both synthetic and secretory levels within the early stage of HDS.