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This Article Full Text Full Text (PDF) All Versions of this Article: 585/1/217    most recent jphysiol.2007.138818v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Newman, J. M. B. Articles by Rattigan, S. Search for Related Content PubMed PubMed Citation Articles by Newman, J. M. B. Articles by Rattigan, S. Related Collections Skeletal Muscle and Exercise

¹ Biochemistry, Medical School, University of Tasmania, Private Bag 58, Hobart 7001, Tasmania, Australia

In the present study, a mathematical model using the microdialysis outflow: inflow (O/I) ratio of the novel analogue L-[¹⁴C]glucose has been developed which allows the calculation of the nutritive (and non-nutritive) flow in muscle as a proportion of total blood flow. Anaesthetized rats had microdialysis probes carrying L-[¹⁴C]glucose inserted through a calf muscle group (tibialis/plantaris/gastrocnemius). The nutritive fraction of total blood flow was determined under basal conditions and in response to contraction (electrical field stimulation), insulin (hyperinsulinaemic euglycaemic clamp with 10 mU min^–1 kg^–1 insulin) or saline control from limb blood flow and the microdialysis O/I ratio of L-[¹⁴C]glucose. Both contraction and insulin infusion decreased the O/I ratio of L-[¹⁴C]glucose and increased total limb blood flow. Calculations based on mathematical models using L-[¹⁴C]glucose O/I and limb blood flow revealed that during basal conditions, the nutritive fraction of total flow was 0.38 ± 0.06, indicating that basal flow was predominantly non-nutritive. Contraction and insulin increased the nutritive fraction to 0.82 ± 0.24 (P < 0.05) and 0.52 ± 0.12 (P < 0.05). Thus the increase in limb blood flow from insulin was fully accommodated by nutritive flow, while contraction increased nutritive flow at the expense of non-nutritive flow. This novel method using microdialysis and the O/I ratio of L-[¹⁴C]glucose allows the determination of the nutritive fraction of total flow in muscle as well as the proportion of total flow that may be redistributed in response to contraction and insulin.

(Received 17 June 2007; accepted after revision 17 September 2007; first published online 20 September 2007)
Corresponding author J. M. B. Newman: Biochemistry, Medical School, University of Tasmania, Private Bag 58, Hobart 7001, Tasmania, Australia. Email: j.newman{at}utas.edu.au