ADRENALINE INCREASES THE UPTAKE OF LOW-DENSITY LIPOPROTEINS IN CAROTID ARTERIES OF RABBITS

The uptake of low-density lipoprotein was compared in carotid arteries of anaesthetized male New Zealand rabbits after infusing alternate carotids with adrenaline. or with saline as a control. The infusions were at approximately 2% of the carotid blood flow, the adrenaline being at approximately 10 nM in the carotid blood. Human low density lipoprotein, methylated to prevent recognition by the high affinity receptor (m-LDL), was labelled with I-125 and injected intravenously. Adrenaline infusions for 2 or 4 h significantly increased m-LDL radioactivity in the carotid walls. The radioactivity of reinjected red cells labelled with Cr-51 was the same in the walls of both carotids. This excluded the possibility that the excess LDL radioactivity in adrenaline infused carotids was accounted for by increased amounts of blood in the arterial wall. It also made it improbable that the excess LDL resulted from decreased elimination through a vasoconstriction effect of adrenaline on the vasa vasorum, which should have decreased the amount of radioactivity due to red cells. The results, therefore, suggest that adrenaline at its pathophysiological blood concentrations accelerates the uptake of LDL by large arteries in rabbits.