Augmented Tissue Oxygen Supply during Striated Muscle Contraction in the Hamster: Relative Contributions of Capillary Recruitment, Functional Dilation, and Reduced Tissue PO2

To investigate the relative contributions of alterations in blood flow, capillary density, and tissue PO to elevated oxygen delivery in working muscle, we conducted experiments on the suffused hamster cremaster muscle, using in vivo microscopic techniques. Muscle PO was measured during striated musc...

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Veröffentlicht in:Circulation research 1982-12, Vol.51 (6), p.711-721
Hauptverfasser: Klitzman, Bruce, Damon, David N, Gorczynski, Richard J, Duling, Brian R
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Sprache:eng
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Zusammenfassung:To investigate the relative contributions of alterations in blood flow, capillary density, and tissue PO to elevated oxygen delivery in working muscle, we conducted experiments on the suffused hamster cremaster muscle, using in vivo microscopic techniques. Muscle PO was measured during striated muscle twitch contraction at 1 Hz. Tissue oxygenation was changed by using suffusion solutions equilibrated with 0%, 5%, 10%, 21%, or 50% oxygen. Contraction caused an increase in capillary density (capillary recruitment), whose magnitude was related to the equilibration gas and, thus, to the suffusate PO. Capillary recruitment first increased as the oxygen content was raised, peaked with 10% oxygen, and then diminished with higher oxygen content. Arteriolar functional dilation was also observed; when oxygen was raised above 21%, dilation was decreased. The data suggest that oxygen supply is increased primarily by arteriolar conductance changes with low suffusion solution oxygen (0% to 5%), and by capillary recruitment and increased PO gradients above 10% oxygen. When vasomotor tone was increased by addition of norepinephrine to the suffusion medium, the changes observed were similar to those observed when oxygen was increased. Therefore, we propose that the altered microvascular responses during vasoconstriction are a function of vascular tone rather than the levels of tissue PO. A model is proposed which may partially explain the relations among vascular tone, functional dilation, and capillary recruitment. Our data also suggest that tissue PO may not be precisely regulated about a narrowly defined set point in this striated muscle but that, instead, tissue PO is a dependent variable controlled by the integrated effects of capillary recruitment, functional vasodilation, and altered metabolism.
ISSN:0009-7330
1524-4571
DOI:10.1161/01.RES.51.6.711