Vascular recruitment in skeletal muscle during exercise and hyperinsulinemia assessed by contrast ultrasound.
The purpose of this study was to noninvasively quantify the effects of insulin on capillary blood volume (capBV) and RBC velocity (V(RBC)) in skeletal muscle in vivo with the use of contrast-enhanced ultrasound. We performed contrast ultrasound of the rat hindlimb adductor muscles at baseline and after 2-h infusions of either insulin (3 or 40 mU x kg(-1) x min(-1)) or saline. Saline-treated animals were also studied during contractile exercise. V(RBC) and capBV were calculated from the relation between pulsing interval and video intensity. Femoral artery blood flow, measured by a flow probe, increased with both contractile exercise and insulin. Contractile exercise increased capBV more than twofold and V(RBC) fivefold. Insulin also increased capBV more than twofold in a dose-dependent fashion but did not significantly alter V(RBC). Saline infusion did not significantly alter capBV, V(RBC), or femoral artery blood flow. We conclude that physiological changes in skeletal muscle capillary perfusion can be assessed in vivo with the use of contrast-enhanced ultrasound. Exercise increases both V(RBC) and capBV, whereas hyperinsulinemia selectively increases only capBV, which may enhance skeletal muscle glucose uptake.
Dawson
Dana
D
Cardiovascular Division, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Vincent
Michelle A
MA
Barrett
Eugene J
EJ
Kaul
Sanjiv
S
Clark
Andrew
A
Leong-Poi
Howard
H
Lindner
Jonathan R
JR
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D001810:Blood Volume / Q000187:drug effects; D002196:Capillaries; D004912:Erythrocytes; D005263:Femoral Artery; D005947:Glucose / Q000378:metabolism; D006946:Hyperinsulinism / Q000503:physiopathology*; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000378:metabolism; D005082:Physical Exertion; D051381:Rats; D017207:Rats, Sprague-Dawley; D014463:Ultrasonography
D007328:Insulin; D005947:Glucose