Lipogenesis in the pigeon: in vivo studies

Abstract

Glucose-U-14C was injected into fasted-refed pigeons and the amount of 14C into corporated into the fatty acids of liver, adipose tissue, and blood was determined at intervals thereafter up to 2 hr.Blood glucose and its radioactivity were monitored throughout the experiment. Significant incorporation of glucose carbon into the fatty acids of liver occurred within 3 min. and liver content of radioactive fatty acids reached more or less a plateau at 15 min. Significant appearance of labeled fatty acids in blood and adipose tissue was first seen at 15 min. and their concentrations then rose continuously throughout the experimental period. Incorporation of glucose carbon into glyceride-glycerol of plasma and adipose tissue was determined. The ratio of counts in glyceride-fatty acids to glyceride-glycerol remained close to unity in plasma throughout the experiment but rose progressively to a value of 7.0 at 2 hr. in adipose tissue. It is concluded that in the pigeon the liver is the chief site of fatty acid synthesis from glucose and may account for as much as 96% of the total lipogenesis. It would appear that adipose tissue derives its glyceride-fatty acids from plasma triglyceride and its glyceride-glycerol from plasma glucose.