Plasma free fatty acid levels during cold-induced and noradrenaline-induced nonshivering thermogenesis in the Djungarian hamster.

In Djungarian hamsters the cold-induced thermoregulatory heat production was preceded and accompanied by an increase in the plasma level of free fatty acids. In warm-acclimated hamsters this increase was found more pronounced (0.85 to 1.48 mM) than in cold-acclimated hamsters (0.64 to 0.88 mM). Noradrenaline-induced thermogenesis at thermoneutrality provoked a similar increase in the free fatty acid level. Inhibition of nonshivering thermogenesis during cold exposure by propranolol abolished the increase in free fatty acids completely. The surgical removal of brown adipose tissue proportionately reduced the increase in free fatty acids. This indicates that the rise in plasma free fatty acids is functionally related to nonshivering thermogenesis and originates from brown adipose tissue.