Journal of Applied Physiology, Vol 43, Issue 6 1007-1011, Copyright © 1977 by American Physiological Society
Lipolysis in brown adipose tissue of cold- and heat-acclimated hamsters
T. Rabi, Y. Cassuto and A. Gutman
Rates of release of free fatty acids (FFA) and glycerol to the incubation
medium by brown adipose tissue (BAT) slices isolated from heat-acclimated
(H), cold-acclimated (C), and control (N) hamsters in the absence or
presence of epinephrine (E) were studied. Rates of FFA and glycerol release
by tissue slices isolated from H and N animals were similar. In tissue
slices isolated from C animals rate of release of FFA and glycerol was
three times as high. Addition of E to the incubation medium (200
microgram/ml) had no effect on the rate of FFA and glycerol release of
slices from C animals, but tripled the rates of slices from N, resulting in
similar values for the two groups. In slices from H animals the rate of
release was lower than in the other two groups, increasing only 1.5-fold.
Pretreatment of N animals with triiodothyronine (T3; 0.8 microgram/100 g
daily for 7 days) doubled the rates of FFA and glycerol release. Addition
of E to the medium affected both pretreated and nontreated slices
similarly. Two possible mechanisms by which temperature acclimation
controls the lipolytic rate of BAT are suggested by 1) the concentration of
specific enzymes and 2) cellular metabolites and hormones which activate
existing systems. It seems that both operate in temperature-acclimated
hamsters.
