Adipocyte size and number in dietary obesity resistant and susceptible rats.

Fat depot cellularity was assessed in overfed dietary obesity resistant S 5B/Pl (S) and susceptible Osborne-Mendel (OM) rats. Cell number and lipid per cell were determined for three fat depots in both 24- and 105-day-old rats. Between these two ages, fat cell number doubled in inguinal fat depots of S rats fed high- or low-fat diets and OM rats fed a low-fat diet, but quadrupled in OM rats fed a high-fat diet. The size of adipocytes in this depot was influenced by strain but not by diet. Compared to normal weight S rats, 24-day-old overfed S rats had twice as many adipocytes in the perirenal-retroperitoneal fat depot. Overfed OM rats had 3 times perirenal-retroperitoneal fat depot. Overfed OM rats had 3 times as many. In OM rats fed the high-fat diet, there was a 16-fold increase in adipocyte number between 24 and 105 days of age. Overfeeding caused a slight increase in perirenal-retroperitoneal adipocyte size in 24-day-old rats but had little influence on cell size in 105-day-old rats.