HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Lo, A. Articles by Secomb, T. W. Search for Related Content PubMed PubMed Citation Articles by Lo, A. Articles by Secomb, T. W.

Theoretical simulation of K⁺-based mechanisms for regulation of capillary perfusion in skeletal muscle

¹Program in Applied Mathematics, University of Arizona, Tucson 85721; and ²Department of Physiology, University of Arizona, Tucson, Arizona 85724

Submitted 19 March 2004 ; accepted in final form 7 April 2004

Muscle fibers release K⁺ into the interstitial space upon recruitment. Increased local interstitial K⁺ concentration ([K⁺]) can cause dilation of terminal arterioles, leading to perfusion of downstream capillaries. The possibility that capillary perfusion can be regulated by vascular responses to [K⁺] was examined using a theoretical model. The model takes into account the spatial relationship between functional units of muscle fiber recruitment and capillary perfusion. Diffusion of K⁺ in the interstitial space was simulated. Two hypothetical mechanisms for vascular sensing of interstitial [K⁺] were considered: direct sensing by arterioles and sensing by capillaries with stimulation of feeding arterioles via conducted responses. Control by arteriolar sensing led to poor tissue oxygenation at high levels of muscle activation. With control by capillary sensing, increases in perfusion matched increases in oxygen demand. The time course of perfusion after sudden muscle activation was considered. Predicted capillary perfusion increased rapidly within the first 5 s of muscle fiber activation. The reuptake of K⁺ by muscle fibers had a minor effect on the increase of interstitial [K⁺]. Uptake by perfused capillaries was primarily responsible for limiting the increase in [K⁺] in the interstitial space at the onset of fiber activation. Vascular responses to increasing interstitial [K⁺] may contribute to the rapid increase in blood flow that is observed to occur after the onset of muscle contraction.

motor units; microvascular units; interstitial space; oxygen diffusion; blood flow regulation