Photoperiod-dependent fat pad mass and cellularity changes
following partial lipectomy in siberian hamsters.
Mauer, Mary Margaret, and Timothy J. Bartness.
Biology and Psychology Departments, Neurobiology Program and
Neuropsychology and Behavioral Neuroscience Program, Georgia State
University, Atlanta, GA 30303
APStracts 2:0241R, 1995.
Long day(LD)-housed Siberian hamsters show compensatory mass increases
in non-excised white adipose tissue (WAT) after partial lipectomy,
whereas hamsters exposed to short days(SD) for 22 weeks do not. The
purpose of this experiment was to determine the cellularity changes
underlying WAT compensation and whether the duration of SD exposure
affects compensation. Male Siberian hamsters were epididymal(E) or
inguinal(I) WAT lipectomized(x) or sham-lipectomized(SHAM) and either
remained in LDs or were transferred to SDs and killed 6 or 12 weeks
later. In LDs, lipectomized hamsters showed compensatory mass
increases in retroperitoneal WAT(RWAT) due to hyperplasia. IWAT mass
also was increased by 40% in LD-housed EWATx hamsters due to non
-significant increases in adipocyte size and number at weeks 6 and 12,
respectively. SD-housed hamsters responded to lipectomy by delaying
the SD-associated body fat loss such that RWAT mass was reduced only
one-third as much in lipectomized as in SHAM hamsters and the IWAT
adipocytes of EWATx hamsters were larger than in SHAM hamsters at
week 6. At week 12, there was little indication of fat pad
compensation by SD-housed hamsters. Collectively, the results of the
present experiment and our previous study (16) suggest that the
inhibitory effect of SDs on fat pad compensation after lipectomy
increases with prolonged SD exposure.
Received 24 April 1995; accepted in final form 22 August 1995.
APS Manuscript Number R251-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 15 September 1995.