AJP - Endocrinology and Metabolism, Vol 244, Issue 4 323-E328, Copyright © 1983 by American Physiological Society
Restraint-induced thermogenesis blunted by fasting in rats
M. Hayashi
Physical restraint was performed in fasted (F3, fasted for 3 days; F7,
fasted for 7 days), and fed control (C) rats. In contrast to the C group,
the F3 and F7 groups showed a low resting metabolism and a low calorigenic
response to restraint. During restraint, plasma levels of norepinephrine
(NE) and epinephrine (E) were markedly increased but were not significantly
different between the C and F7 groups. Calorigenic responses to NE and E
(6.0 and 12.0 nmol X kg-1 X min-1) were significantly less in the F3 and F7
groups than in the C group. Plasma concentrations of glucose were increased
by the infusion of catecholamines in the C and F7 groups. The values were
not different between the two groups. Plasma levels of free fatty acid in
the F7 group were significantly higher than in the C group before and
during catecholamine infusion. Plasma concentrations of thyroxine and
triiodothyronine were significantly less in the F7 group than in the C
group. The blunted restraint-induced thermogenesis in fasted rats may be
mainly attributed to the decreased calorigenic response to catecholamines.
The decreased calorigenic response may be due to suppressed utilization of
energy substrates in calorigenic tissues produced by the lowered activity
of thyroid hormone.
