期刊
RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY
卷 146, 期 2-3, 页码 259-268出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.resp.2004.12.009
关键词
microvascular oxygen pressures; muscle contraction; microvascular oxygen pressure; Fick's law
资金
- NHLBI NIH HHS [HL50306, HL71270] Funding Source: Medline
- NIA NIH HHS [AG19228] Funding Source: Medline
Aging alters skeletal muscle vascular geometry and control such that the dynamics of muscular blood flow (0) and 02 delivery ((Q) over dot O-2) may be impaired across the rest-exercise transition. If, at the onset of muscle contractions, 0 dynamics are slowed disproportionately to those of muscle O-2 uptake ((V) over dot O-2), microvascular PO2 (PO(2)m) would be reduced and blood-tissue 0, transfer compromised. This investigation determined the effects of aging on PO(2)m (a direct reflection of the (Q) over dot O-2-to-(V) over dot O-2 ratio), at rest and across the rest-contractions transition in the spinotrapezius of young (similar to 6 months, n = 9) and old (> 24 months, n = 10) male Fisher 344/Brown Norway hybrid rats. Phosphorescence quenching techniques were used to quantify PO(2)m, and test the hypothesis that, across the rest-contractions (twitch, 1 Hz; 4-6 V, 240 s) transition, aging would transiently reduce the (Q) over dot O-2-to-(V) over dot O-2 ratio causing a biphasic profile in which PO(2)m fell below steady-state contracting values. Old rats had a lower pre-contraction baseline PO(2)m than young (27.1 +/- 1.9 versus 33.8 +/- 1.6 mmHg, P < 0.05, respectively). In addition, in old rats PO(2)m demonstrated a pronounced difference between the absolute nadir and end-contracting values (2.5 +/- 0.9 mmHg), which was absent in young rats. In conclusion, unlike their young counterparts, old rats exhibited a transiently reduced PO(2)m across the rest-contractions transition that may impair blood-tissue O-2 exchange and elevate the O-2 deficit, thereby contributing to premature fatigue. (c) 2004 Elsevier B.V. All rights reserved.
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