Evidence of enhanced storage capacity in adipose tissue of genetically fat chickens.

The storage capacity for plasma triglyceride in abdominal adipose tissue has been investigated in two lines of chickens selected for either high or low adiposity (fat line and lean line, respectively). Adipose tissue cellularity and lipoprotein lipase (LPL) activity were estimated in 2- and 5-wk-old birds. In 2-wk-old birds, cellularity and LPL and glycerophosphate dehydrogenase (GPDH) activity were evaluated in the stromavascular fraction. At both ages studied, the fat line exhibited a twofold increase in mature fat cell number and a marked hypertrophy. LPL activity per cell did not differ with genotype, regardless of the nutritional state; however, LPL activity per whole fat pad was higher in fat birds. In 2-wk-old fat chickens, the stromavascular fraction was characterized by an increase in cell number and a decrease in LPL activity, while GPDH was unchanged. Finally, adipocyte hyperplasia in the fat line appeared to reflect an excessive proliferation of precursor cells. The higher LPL activity in fat birds resulted mainly from cell hyperplasia, rather than from a greater intrinsic activity of adipocytes. Consequently, enhanced fatty acid uptake by adipose tissue represents a major factor in determination of adiposity in the chicken.