Fig. 4. Episodic hypoxia increases HIF-1α protein levels. Western blot analysis of HIF-1α protein levels (top panel) in (A) mouse renal cells (DCT) and (B) human fibrosarcoma cells (HT1080). Quantitation of the data is shown in the bottom panel. Detection of tubulin served as a loading control. Error bars indicate standard deviation (n=3). Significance to normoxia ##: p<0.01, ###: p<0.001. Asterisks denote significance between hypoxic groups. *: p<0.05.