Muscle blood flow response to mental stress and adrenaline infusion in man: microdialysis ethanol technique compared to (133)Xe clearance and venous occlusion plethysmography.
OBJECTIVE
Adrenaline, administered locally by microdialysis in skeletal muscle, causes vasoconstriction around the microdialysis catheter. This is contrary to the vasodilation that normally occurs when adrenaline is infused intravenously or intra-arterially. The hypothesis was tested that vasoconstriction, measured by microdialysis, would not occur with two interventions causing increased plasma levels of adrenaline, mental stress and intravenous adrenaline infusion (0.1 nmol kg(-1) min(-1)).


METHODS
Twenty-four men (27 +/- 1.6 years) underwent these interventions. Blood flow was determined by the microdialysis ethanol technique and (133)Xe clearance (gastrocnemius muscle, medial head) and by venous occlusion plethysmography (calf).


RESULTS
The ethanol outflow/inflow ratio, which is inversely related to blood flow, decreased to 92.0 +/- 3.4% of basal, P = 0.014 (mean +/- SEM, n = 16) during the mental stress test, but increased to 108.3 +/- 2.2% of basal, P = 0.001 (n = 16) during the adrenaline infusion. The latter increase was abolished when adrenaline was infused during alpha-receptor blockade by phentolamine. On the contrary, by (133)Xe clearance and venous occlusion plethysmography, blood flow increased during both interventions; 2.0-1.7-fold (mental stress) and 1.3-1.4-fold (adrenaline infusion), respectively, P<0.05.


CONCLUSIONS
Adrenaline causes vasoconstriction in skeletal muscle when blood flow is measured with the microdialysis ethanol technique, irrespective of the mode of administration. The discrepant blood flow result obtained with the microdialysis ethanol technique might, at least partly, be explained by differential diffusion properties of ethanol and (133)Xe. An additional or alternative explanation might be that an inserted microdialysis catheter shifts the balance of vasoconstrictor and vasodilator effects of adrenaline in skeletal muscle.
Widegren
U
U
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Hickner
R C
RC
Jorfeldt
L
L
Henriksson
J
J
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000328:Adult; D002492:Central Nervous System Depressants; D004837:Epinephrine / Q000008:administration & dosage* / Q000097:blood; D000431:Ethanol; D006339:Heart Rate; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D017551:Microdialysis / Q000379:methods*; D018482:Muscle, Skeletal / Q000098:blood supply*; D010646:Phentolamine / Q000008:administration & dosage; D010991:Plethysmography / Q000379:methods*; D011877:Radionuclide Imaging; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology*; D013315:Stress, Psychological / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000097:blood; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000097:blood; D014680:Veins / Q000502:physiology; D014980:Xenon Radioisotopes
D000317:Adrenergic alpha-Antagonists; D002492:Central Nervous System Depressants; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D014980:Xenon Radioisotopes; D000431:Ethanol; D004837:Epinephrine; D010646:Phentolamine