Mm. Mauer et Tj. Bartness, PHOTOPERIOD-DEPENDENT FAT PAD MASS AND CELLULARITY CHANGES AFTER PARTIAL LIPECTOMY IN SIBERIAN HAMSTERS, American journal of physiology. Regulatory, integrative and comparative physiology, 39(2), 1996, pp. 383-392
Long day (LD)-housed Siberian hamsters show compensatory mass increase
s in nonexcised white adipose tissue (WAT) after partial lipectomy, wh
ereas hamsters exposed to short days (SDs) for 22 wk do not. The purpo
se of this experiment was to determine the cellularity changes underly
ing lipectomy-induced WAT compensation and whether the duration of SD
exposure affects this compensation. Male Siberian hamsters were epidid
ymal (E) or inguinal (I) WAT lipectomized (x) or sham-lipectomized (Sh
am) and either remained in LDs or were transferred to SDs and killed 6
or 12 wk later. In LDs, lipectomized hamsters showed compensatory mas
s increases in retroperitoneal WAT (RWAT) due to hyperplasia. IWAT mas
s also was increased by similar to 40% in LD-housed EWATx hamsters bec
ause of nonsignificant 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 so that RWAT mass was reduced
only one-third as much in lipectomized as in Sham hamsters, and the I
WAT adipocytes of EWATx hamsters were larger than in Sham hamsters at
week 6. At week 12, there was little indication of fat pad compensatio
n by SD-housed hamsters. Collectively, the results of the present expe
riment and our previous study (16) suggest that the inhibitory effect
of SDs on fat pad compensation after lipectomy increases with prolonge
d SD exposure.