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First published online on March 31, 2006.
Copyright © 2006 by The Physiological Society
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Received January 4, 2006
Revised February 7, 2006
Accepted after revision March 26, 2006

Temporal profile of skeletal muscle capillary hemodynamics during recovery from contractions

Leonardo F Ferreira1, Danielle J Padilla1, Timothy I Musch1, and David C Poole1*

1 Kansas State University

* To whom correspondence should be addressed. E-mail: poole{at}vet.k-state.edu.

In skeletal muscle capillaries, red blood cell flux (FRBC), velocity (VRBC) and hematocrit (HctCAP) are key determinants of microvascular O2 exchange. However, the mechanisms entailing the changes in FRBC, VRBC and HctCAP during muscle contractions and recovery thereafter are not fully understood. To address this issue we used intravital microscopy to investigate the temporal profile of the rat spinotrapezius muscle (n = 5) capillary hemodynamics during recovery from 3 min of twitch muscle contractions (1 Hz, 4-6 V). Specifically, we hypothesized that 1) during early recovery FRBC and VRBC would decrease rapidly and FRBC would display a biphasic response (consistent with a muscle-pump effect on capillary hemodynamics); and 2) there would be a dynamic relationship between changes ({Delta}) in VRBC and HctCAP. The values at rest (R) and end-recovery (ER) were significantly lower (P < 0.05) than at end-contraction (EC) for FRBC (in cell/s, R = 30.1 ± 7.8, EC = 46.2 ± 7.3 and ER = 26.0 ± 6.1), VRBC (in µm/s, R = 368 ± 83, EC = 497 ± 62 and ER = 334 ± 59) and HctCAP (R = 0.193 ± 0.016, EC = 0.214 ± 0.023 and ER = 0.185 ± 0.019). The first data point where a significant decrease in FRBC, HctCAP and VRBC occurred was at 5, 5 and 20 s post- contraction, respectively. The decrease in FRBC approximated a monoexponential response (half-time of ~ 26 s). The relationship between {Delta}VRBC and {Delta} HctCAP was not significant (P > 0.05). Based on the early decrease in FRBC (within 5 s), overall dynamic profile of FRBC and the ~ 20 s ‘delay’ to the decrease in VRBC we conclude that the muscle- pump does not appear to contribute substantially to the steady-state capillary hemodynamics in the contracting rat spinotrapezius muscle. Moreover, our findings suggest that alterations in VRBC do not obligate proportional changes in HctCAP within individual capillaries following muscle contractions.


Key words: Blood flow • Exercise • Microcirculation




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