EFFECTS OF NORADRENALINE AND THE BLOOD PERFUSION RATE ON THE OXYGEN-CONSUMPTION OF INTACT AND ISOLATED MUSCLES OF COLD-ACCLIMATED RATS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 29  (2) , 151-160
Abstract
The effect of the blood perfusion rate and of noradrenaline [norepinephrine (NA)] on the O2 consumption of the isolated hind limb and on the partly, and vascularly completely, isolated cranial gracilis muscle of cold-acclimated rats was studied. O2 consumption of the limb was stimulated by a raised perfusion rate together with growth of the O2 extraction coefficient and by NA, which also raised O2 consumption when the perfusion rate was constant. O2 consumption of the partly isolated muscle was likewise stimulated by a raised perfusion rate, but without a simultaneous increase in the O2 extraction coefficient. In the vascularly completely isolated muscle, a raised perfusion rate had only a transient stimulant effect on O2 consumption. In the partly and the completely isolated muscle, NA raised the arteriovenous difference in the blood O2 content and organ resistance independently of each other. The calorigenic effect of NA, which was determined by the ratio of the 2 effects, did not exceed 34% above the resting level. The thermogenesis of resting muscle can be controlled by the blood flow on the basis of a mechanism other than the limitation of O2 or substrate supply. NA acts independently of O2 extraction from the blood and of the blood flow. The blood flow is a mechanism at the organ level, which participates in the control of nonshivering thermogenesis in skeletal muscle.