Starvation in the rat. I. Effect of age and obesity on organ weights, RNA, DNA, and protein.

Previous studies have shown that obese man adapts to prolonged starvation with a conservation of body protein. In an attempt to delineate the biochemical and hormonal changes responsible for this adaptation, the effect of starvation was studied in rats with differing abilities to survive a fast and conserve protein. Sixteen-week-old rats made obese by fat feeding survived starvation for 25-30 dys, whereas 16-wk-old controls survived 11-12 days and the 8-wk-old controls for 6-7 days. Starvation decreased hepatic weight, RNA, and protein early in the fast in all three groups. In heart, the extensor digitorum longus muscle and some other organs decreases in RNA, protein, and weight occurred more slowly and were smaller in magnitude in the 16-wk-old control and obese rats. A pronounced loss of cardiac protein and RNA occurred in the 8-wk-old group. We conclude that 16-wk-old control and obese rats are better able to survive and conserve organ protein and RNA during prolonged starvation than younger rats. To what extent this reflects differences in the age and to what extent differences in adiposity remains to be determined.