Effect of gold thioglucose-induced obesity on adipose tissue weight and cellularity in male and female mice suckled in large and small litters: investigations into sex differences and site differences.

1. Over- or undernutrition of newborn mice was caused by suckling in litters consisting initially of four or eighteen pups. After weaning, mice were fed ad lib. At 13 weeks some mice received gold thioglucose (GTG, 600 mg/kg, intraperitoneally) to induce hyperphagia, and all were killed at 39 weeks. 2. Mice suckled in small litters were heavier, with more body fat and protein. GTG treatment induced rapid weight gain and treated mice from large litters were heavier than untreated mice from small litters. However, the effect of litter size was not totally removed since GTG-treated small-litter mice were heavier than GTG-treated large-litter mice and had more fat, although body protein was not different. 3. Fat distribution between the depots was related to total body fatness and not to the treatment. 4. In male mice, preweaning undernutrition resulted in smaller fat depots containing smaller cells. GTG treatment of large-litter mice restored both to the levels found in small-litter mice: the depots of the latter mice were not significantly different after treatment. 5. In female mice, preweaning undernutrition resulted not only in smaller depots and cells but also fewer cells in all depots except mesenteric. GTG-treatment caused larger depots and cells in all mice with no difference in cell size whether mice were from large or small litters. The number of cells in the perirenal and mesenteric depots was greater in GTG-treated mice and was the same whether mice were from large or small litters. 6. We conclude that the level of preweaning nutrition does not affect the ability of adipose tissue to develop subsequently through hypertrophy or hyperplasia of the adipocytes or both, given a sufficient energy surplus consisting of normal pelleted feed, low in lipid.