EFFECTS OF NOREPINEPHRINE ON UPTAKE AND OXIDATION OF PLASMA FREE FATTY ACIDS IN COLD-ACCLIMATED RATS

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Abstract
To know the mode of action of norepinephrine [NE] in enhanced utilization of plasma free fatty acids (FFA) in cold acclimation, albumin-bound 14C-palmitate was infused i.v. at a constant rate into cold- and warm-acclimated rats under pentobarbital anesthesia with and without NE infusion. Rectal temperature, CO2 output and plasma FFA, from which the rates of FFA uptake and oxidation were calculated, were determined simultaneously. Similar fractions, i.e., 7 and 5% of the total uptake of plasma FFA by the tissue, were immediately oxidized in both cold- and warm-acclimated rats, respectively. NE infusion caused a significant increase in all parameters examined. During hormone infusion the percentage of FFA uptake oxidized was elevated from 22% in control to 50% in cold-acclimated rats. This increment was accompanied by greater increases in rectal temperature and CO2 output. In functionally eviscerated cold-acclimated rats, NE induced a greater increase in the percentage of FFA oxidized than in eviscerated controls. Although the FFA uptake was increased simultaneously, NE infusion caused a more marked acceleration of the oxidation of plasma FFA in the cold-acclimated rats than in control rats.