Tissues can be exposed to CH in several circumstances including pulmonary diseases and high altitude exposure. We evaluated the expression level of 2 O₂TF, the key cellular HIF1a, and the oxidative mitochondrial activity related PGC1a, in rat model of CH (10% O₂ for 3 weeks). Tissue samples from upper and lower lung lobes, left and right ventricles, soleus and extensor digitorum longus (EDL) were collected 2–4 hrs from the end of CH; HIF1a and PGC1a expression were evaluated by western blot.

Results from CH samples expressed normalized to a-tubulin and relative to normoxic condition, reveal a significant increase in O₂TF for adaptation to CH in the right ventricle (1.48 for HIF1a and 1.4 for PGC1a) and in the lung (1.79 and 1.85 for the HIF1a in the upper and lower lobe respectively) with a significant greater expression of PGC1a in the lower lobe (1.83 and 2.98 upper vs lower, p<0.05). The involvement of the cardio-pulmonary compartment can be related to the increase in pulmonary vascular resistances and in lung tissue/vascular remodeling in CH that was previously shown to be more pronounced in the lower lobe (Rivolta et al. ERJ, 2011). No differences were detected for left ventricle, EDL (predominant white fibers muscle) and soleus (predominant red fibers muscle).