Increased fiber capillarization in flight muscle of finch at altitude.

摘要

We examined fiber capillarization and ultrastructure in the highly aerobic flight muscle of six gray crowned rosy finches (Leucosticte arctoa; mass 22.9 +/- 0.5 (SE) g) living at altitude (A; White Mountains of Eastern California; 4000 m) compared to eight sea-level (SL) house finches (Carpodacus mexicanus, mass, 19.8 +/- 0.6 g) of the same subfamily, Carduelinae. Capillary length per fiber volume (A, 10,400 +/- 409 mm(-2); SL, 7513 +/- 423; P < 0.001) and capillary-to-fiber ratio (A, 2.32 +/- 0.07; SL, 1.85 +/- 0.06; P < 0.001) were significantly greater in A, with no difference in fiber cross-sectional area compared to SL. Capillary geometry was significantly different in A, yielding a greater contribution of tortuosity and branching to capillary length than in SL. Capillary-to-fiber surface ratio and fiber mitochondrial volume were both greater in A, but their ratio was similar to SL, indicating a proportional increase in the size of the capillary to fiber interface and fiber mitochondrial volume in A to sustain high levels of aerobic capacity while living at altitude.