The ethanol technique of monitoring local blood flow changes in rat skeletal muscle: implications for microdialysis

Abstract

We have investigated the feasibility of monitoring local skeletal muscle blood flow in the rat by including ethanol in the perfusion medium passing through a microdialysis probe placed in muscle tissue. Ethanol at 5, 55, or 1100 mM did not directly influence local muscle metabolism, as measured by dialysate glucose, lactate, and glycerol concentrations. The clearance of ethanol from the perfusion medium can be described by the outflow/inflow ratio ([ethanol]collected dialysate/[ethanol]infused perfusion medium), which was found to be similar (between 0.36 and 0.38) at all ethanol perfusion concentrations studied. With probes inserted in a flow-chamber, this ratio changed in a flow-dependent way in the external flow range of 5-20 microliters min-1. The ethanol outflow/inflow ratio in vivo was significantly (P less than 0.001) increased (to a maximum of 127 +/- 2.8% and 144 +/- 7.4% of the baseline, mean +/- SEM) when blood flow was reduced by either leg constriction or local vasopressin administration, and significantly (P less than 0.001) reduced (to 62 +/- 6.4% and 43 +/- 4.4% of baseline) with increases in blood flow during external heating or local 2-chloroadenosine administration, respectively. Dialysate glucose concentrations correlated negatively with the ethanol outflow/inflow ratio (P less than 0.01) and consequently decreased (to 46 +/- 7.6% and 56 +/- 5.6% of baseline) with constriction and vasopressin administration and increased (to 169 +/- 32.5% and 262 +/- 16.7% of baseline) following heating and 2-chloroadenosine administration. Dialysate lactate concentrations were significantly increased (approximately 2-fold, P less than 0.001) during all perturbations of blood flow. In conclusion, this technique makes it possible to monitor changes in skeletal muscle blood flow; however, methods of quantification remain to be established. The fact that blood flow changes were found to significantly affect interstitial glucose and lactate concentrations as revealed by microdialysis indicates that this information is critical in microdialysis experiments.

Interstitial glucose and lactate balance in human skeletal muscle and adipose tissue studied by microdialysis.

“…This has been verified in a large number of studies in the brain (for a detailed account, see Ungerstedt, 1991), and in adipose tissue and skeletal muscle of anaesthetized animals (Arner, Bolinder, Eliasson, Lundin & Ungerstedt, 1988;Hickner, Rosdahl, Borg, Ungerstedt, Jorfeldt & Henriksson, 1991;Stahle, 1991) as well as in human adipose tissue (Lonnroth, Jansson & Smith, 1987;Bolinder, Hagstr6m, Ungerstedt & Arner, 1989). Furthermore, by including ethanol (5 mM) in the perfusion solution tissue blood flow may be evaluated based on the clearance of ethanol from the probe into the tissue (Hickner et al 1991). Due to its influence on the composition of the interstitial fluid, blood flow is an important variable in microdialysis studies (Hickner, Rosdahl, Borg, Ungerstedt, Jorfeldt & Henriksson, 1992).…”

“…The low flow rate furthermore ensures a low hydrostatic pressure and therefore that the fluid does not pass through the dialysis membrane to the tissue but continues to the outflow side of the probe and can be collected at the outlet. This has been verified in a large number of studies in the brain (for a detailed account, see Ungerstedt, 1991), and in adipose tissue and skeletal muscle of anaesthetized animals (Arner, Bolinder, Eliasson, Lundin & Ungerstedt, 1988;Hickner, Rosdahl, Borg, Ungerstedt, Jorfeldt & Henriksson, 1991;Stahle, 1991) as well as in human adipose tissue (Lonnroth, Jansson & Smith, 1987;Bolinder, Hagstr6m, Ungerstedt & Arner, 1989). Furthermore, by including ethanol (5 mM) in the perfusion solution tissue blood flow may be evaluated based on the clearance of ethanol from the probe into the tissue (Hickner et al 1991).…”

Cholinoceptor‐mediated effects on glycerol output from human adipose tissue using in situ microdialysis

“…A thorough methodological evaluation of this technique was made in vitro and in vivo in skeletal muscle, including a direct comparison with the radioactive xenon-washout technique (Hickner et al, 1992;. These data suggest that changes in the ethanol ratio reflect changes in the flow around the probe in vivo.…”

Atrial Natriuretic Peptide Induces Postprandial Lipid Oxidation in Humans

“…Calculations and statistics. Changes in blood flow were determined using the ethanol dilution technique, which is based on Fick's principle (16,17). Accordingly, a decrease in the outflow-to-inflow ratio is equivalent to an increase in blood flow and vice versa.…”