In:
Journal of Applied Physiology, American Physiological Society, Vol. 88, No. 2 ( 2000-02-01), p. 560-566
Abstract:
Although evidence for muscle O 2 diffusion limitation of maximal O 2 uptake has been found in the intact organism and isolated muscle, its relationship to diffusion distance has not been examined. Thus we studied six sets of three purpose-bred littermate dogs (aged 10–12 mo), with 1 dog per litter allocated to each of three groups: control (C), exercise trained for 8 wk (T), or left leg immobilized for 3 wk (I). The left gastrocnemius muscle from each animal was surgically isolated, pump-perfused, and electrically stimulated to peak O 2 uptake at three randomly applied levels of arterial oxygenation [normoxia, arterial[Formula: see text]([Formula: see text] ) 77 ± 2 (SE) Torr; moderate hypoxia, [Formula: see text]: 33 ± 1 Torr; and severe hypoxia, [Formula: see text] : 22 ± 1 Torr]. O 2 delivery (ml ⋅ min −1 ⋅ 100 g − 1 ) was kept constant among groups for each level of oxygenation, with O 2 delivery decreasing with decreasing [Formula: see text]. O 2 extraction (%) was lower in I than T or C for each condition, but calculated muscle O 2 diffusing capacity (Dm[Formula: see text]) per 100 grams of muscle was not different among groups. After the experiment, the muscle was perfusion fixed in situ, and a sample from the midbelly was processed for microscopy. Immobilized muscle showed a 45% reduction of muscle fiber cross-sectional area ( P 〈 0.05), and a resulting 59% increase in capillary density ( P 〈 0.05) but minimal reduction in capillary-to-fiber ratio (not significant). In contrast, capillarity was not significantly different in T vs. C muscle. The results show that a dramatically increased capillary density (and reduced diffusion distance) after short-term immobilization does not improve Dm[Formula: see text] in heavily working skeletal muscle.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/jappl.2000.88.2.560
Language:
English
Publisher:
American Physiological Society
Publication Date:
2000
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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