Increased sympathetic activity in rat white adipose tissue during
prolonged fasting.
Migliorini, Renato H., Maria A. R. Garofalo, and Isis C. Kettelhut.
Departments of Biochemistry and Physiology, School of Medicine,
USP, Ribeirao Preto, 14049-900, S.P., Brazil
APStracts 3:0329R, 1996.
The effect of prolonged fasting on sympathetic activity was examined
in rat white adipose tissue (WAT) and, for comparison purposes, in
interscapular brown adipose tissue (IBAT). Preliminary experiments
showed that 6-hydroxydopamine or tyramine administration to fed
animals produced similar reductions in norepinephrine (NE) content of
WAT and IBAT. Fasting for 48 hours did not affect tissue NE content
significantly, but induced a threefold increase in 3H-NE uptake by
retroperitoneal and epididymal adipose tissue, contrasting with a 50%
reduction in IBAT. Measured with -methyltyrosine, NE fractional rates
of turnover were faster and calculated turnover rates were three
times higher in retroperitoneal and epididymal tissue from fasted
rats than in tissues from fed controls. In experiments with 3H-NE,
although fractional rates did not change significantly, calculated NE
turnover also increased in retroperitoneal and epididymal tissue
after food deprivation. In contrast, in IBAT NE turnover either did
not change (measured with -methyltyrosine), or, in the experiments
with 3H-NE, decreased significantly after fasting. These and other
data suggest that a centrally controlled selective activation of WAT
sympathetic fibers contributes to fasting lipolysis.
Received 10 April 1996; accepted in final form 26 August 1996.
APS Manuscript Number R202-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996