High-altitude exposure decreases L-ferritin and total iron content in skeletal muscle. The changes in ferritin and iron content in muscle biopsies obtained from vastus lateralis under normoxic conditions at SL and during exposure to HA (4559 m) for 7 to 9 days are shown. (A) Ferritin H and L subunit contents. The amount of H and L subunits in extracts of muscle biopsies was determined by ELISA using monoclonal antibodies against the corresponding recombinant human ferritin subunits. The H- and L-ferritin contents are expressed relative to the value at SL, which was arbitrarily defined as 100. The values are mean ± SE of 4 determinations in 9 participants. (B) Total iron content. The determination was performed by atomic absorption spectrometry. The total muscle iron content (measured in μg/100 mg dry weight) is expressed relative to the value at SL, which was arbitrarily defined as 100. The values are means ± SE for 9 participants. The calculation of statistical differences from normoxia was performed using the Wilcoxon test. *P < .05.