Nutritive blood flow affects microdialysis O/I ratio for [(14)C]ethanol and (3)H(2)O in perfused rat hindlimb.
Changes in the microdialysis outflow-to-inflow (O/I) ratio for [(14)C]ethanol and (3)H(2)O were determined in the perfused rat hindlimb after increases and decreases in nutritive flow mediated by the vasoconstrictors norepinephrine (NE) and serotonin (5-HT), respectively. Microdialysis probes (containing 10 mM [(14)C]ethanol and (3)H(2)O pumped at 1 or 2 microl/min) were inserted through the calf of the rat. Hindlimb perfusion flow rate was varied from 6 to 56 ml x min(-1) x 100 g(-1) in the presence of NE, 5-HT, or saline vehicle. The O/I ratios for both tracers were determined at each perfusion flow rate, as was perfusion pressure, oxygen uptake (a surrogate indicator of nutritive flow), and lactate release. Both tracers showed a decreased O/I ratio as hindlimb perfusion flow was increased, with [(14)C]ethanol being higher than (3)H(2)O. NE decreased the O/I ratio compared with vehicle, and 5-HT increased it for both tracers and both microdialysis flow rates. We conclude that the microdialysis O/I ratio, while able to detect changes in total flow, is also sensitive to changes in nutritive and nonnutritive flow, where the latter still extracts tracer, but less than the former.
Newman
J M
JM
Department of Biochemistry, Medical School, University of Tasmania, Hobart, Australia. j.newman@utas.edu.au
Di Maria
C A
CA
Rattigan
S
S
Clark
M G
MG
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002250:Carbon Radioisotopes; D002492:Central Nervous System Depressants / Q000493:pharmacokinetics*; D000431:Ethanol / Q000493:pharmacokinetics*; D006614:Hindlimb / Q000098:blood supply*; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D018482:Muscle, Skeletal / Q000098:blood supply; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D014316:Tritium; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D014867:Water / Q000378:metabolism*
D002250:Carbon Radioisotopes; D002492:Central Nervous System Depressants; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D014867:Water; D014316:Tritium; D009599:Nitroprusside; D012701:Serotonin; D019344:Lactic Acid; D000431:Ethanol; D009638:Norepinephrine