TEMPORAL CHANGES IN FAT PAD MASS AND CELLULARITY AFTER LIPECTOMY IN SIBERIAN HAMSTERS

Long-day-housed Siberian hamsters show increases in the mass of nonexc ised white adipose tissue GNAT) 12 weeks after bilateral removal (x) o f epididymal WAT (EWAT). Although EWAT shows no significant regenerati on, surviving EWAT appears to increase in mass to a small degree. The purpose of the present study was to determine the time course for fat pad mass and cellularity changes after EWATx and to test whether survi ving EWAT adipocytes undergo hypertrophy or hyperplasia. Male Siberian hamsters underwent EWATx or sham EWATx (SHAM). At Week 0 and at 2-wee k intervals up to 12 weeks postsurgery, a representative sample of ani mals from each group were killed. EWAT, retroperitoneal WAT (RWAT), an d inguinal WAT (IWAT) were removed, weighed, and processed for cellula rity measurement. IWAT and, to a nonsignificant degree, RWAT, increase d in mass after EWATx due to fat cell hypertrophy. These changes began as early as Week 4 postlipectomy, but no mass or cellularity change w as significant until Week 12. The surviving EWAT adipocytes of EWATx h amsters also were larger than those of SHAM hamsters and, unlike EWAT adipocyte number, increased with time within the EWATx group. SHAM ham sters showed slight increases in the mass of EWAT, but not IWAT or RWA T, due to a nonsignificant doubling of EWAT adipocyte number during th e 3 months of the experiment. (C) 1997 Elsevier Science Inc.