MICRODIALYSIS ETHANOL REMOVAL REFLECTS PROBE RECOVERY RATHER THAN LOCAL BLOOD-FLOW IN SKELETAL-MUSCLE

The present study compared the microdialysis ethanol outflow-inflow te chnique for estimating blood flow (BF) in skeletal muscle of humans wi th measurements by Doppler ultrasound of femoral artery inflow to the limb (BFFA) The microdialysis probes were inserted in the vastus later alis muscle and perfused with a Ringer acetate solution containing eth anol, [2-H-3]adenosine (Ado), and D-[C-14(U)]glucose. BFFA at rest inc reased from 0.16 +/- 0.02 to 1.80 +/- 0.26 and 4.86 +/- 0.53 l/min wit h femoral artery infusion of Ado (Ado(FA,i)) at 125 and 1,000 mu g min -l l-l thigh volume (low dose and high dose, respectively; P < 0.05) a nd to 3.79 +/- 0.37 and 6.13 +/- 0.65 l/min during one-legged, dynamic , thigh muscle exercise without and with high AdoFA,i, respectively (P < 0.05). The ethanol outflow-to-inflow ratio (38.3 +/- 2.3%) and the probe recoveries (PR) for [2-3H]Ado (35.4 +/- 1.6%) and for D-[C-14(U) ]glucose (15.9 +/- 1.1%) did not change with AdoFA,i at rest (P = not significant). During exercise without and with AdoFA,i, the ethanol ou tflow-to-inflow ratio decreased (P < 0.05) to a similar level of 17.5 +/- 3.4 and 20.6 +/- 3.2%, respectively (P = not significant), respect ively, while the PR increased (P < 0.05) to a similar level (P = not s ignificant) of 55.8 +/- 2.8 and 61.2 +/- 2.5% for [2-H-3]Ado and to 42 .8 +/- 3.9 and 45.2 +/- 5.1% for D-[C-14(U)]glucose. Whereas the ethan ol outflow-to-inflow ratio and PR correlated inversely and positively, respectively, to the changes in BF during muscular contractions, neit her of the ratio nor PR correlated to the Ado(FA,i)-induced BF increas e. Thus the ethanol outflow-to-inflow ratio does not represent skeleta l muscle BF but rather contraction-induced changes in molecular transp ort in the interstitium or over the microdialysis membrane.