Morphology and cell dynamics of adipose tissue in hypothalamic obese mice.

Morphological and cell kinetic characteristics of the epididymal adipose tissue of obese mice, induced by monosodium glutamate (MSG), were examined in comparison to those of normal mice. Mice treated with MSG for 5 postnatal days became obese after 8 wk of age; adipocytes of the MSG-treated mice were larger than those of normal mice. Heterogeneity was noted in components of the adipose tissue in the obese mice after 24 wk; various-sized adipocytes appeared, and the connective tissue elements increased; necrosis of adipocytes was observed by 36 wk; and mononuclear cells and macrophages infiltrated around the necrotic adipocytes. Such changes were not seen in normal mice. Autoradiographic study with continuous and pulse labeling with [3H]thymidine showed that half the fat cells were replaced in 150-200 days in normal mice and that the turnover rate of adipocytes was more rapid in the obese mice than in the normal mice. In the obese mice, cell death and cell renewal were found to occur more actively.