In this study the HIF-1 signaling pathway was comparatively studied in fast (EDL) and slow (soleus) muscles in basal normoxic conditions and under normobaric hypoxia (10% oxygen). In normoxia HIF-1\u3b1 transcription was determined by Real Time PCR and found similar in EDL and in soleus, whereas HIF-1\u3b1 dependent transcription, explored by Real Time PCR of VEGF which is known as a HIF-1\u3b1 regulated gene and by expression of luciferase under control of a HIF1\u3b1 responsive promoter, was higher in soleus than in EDL muscle. Under normobaric hypoxia conditions, HIF1\u3b1 mRNA showed a small but significant increase in both EDL and soleus and this change was accompanied by an increase of both VEGF transcription and luciferase expression. Interestingly, the time course of the response VEGF and luciferase to hypoxia was different in EDL compared to soleus and, in addition, some discrepancy was detected between VEGF and luciferase pattern. Taken together the results point to diversity between fast and slow muscles in the HIF-1\u3b1 signaling pathway both in normoxic and hypoxic conditions
