Effect of Prior Diet on Lipid Mobilization in Rats During Starvation or Exposure to Cold

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Abstract
Using difference in the lipid content of the epididymal fat pads of the rat as a measure of depot fat changes, an attempt has been made to evaluate the role of previous feeding in the movement of fat out of adipose tissue under the stimuli of fasting or exposure to cold. There was a decreased rate of mobilization when the purified diet, consisting of vitamin-free casein as the protein source, was fed. Rats fed purified diet, however, mobilized fat at a rate equivalent to those fed purina Laboratory Chow when the animals were exposed to 5°. The results indicate that rats fed a purified diet consisting of vitamin-free casein as the protein source mobilize significantly less adipose tissue fat during starvation than did control animals fed a diet of Purina Laboratory Chow; however, the feeding of the purified diet had no influence on the mobilization of lipid during exposure of the animal to 5°. Accordingly, alterations in adipose tissue metabolism which are insensitive to the effect of fasting appear to result from different mechanisms than those which determine the metabolic changes in this tissue subsequent to exposing the animal to a cold environment. The mechanism responsible for the activation of lipase during starvation remains unexplained.