FATS AS ESSENTIAL DIETARY COMPONENTS 853 



olisni of the wliole animal which has previously re('ei\'ed fat is also re- 

 flected in the respiration of isolated tissne from these animals. Thus 

 (lilmore and Samuels'*^ observed that the rate of jrlucose utihzalion in 

 diaphrafi;m tissue removed from animals pre\'iously on a fat diet differed 

 from that of the tissue from rats whi('li had been fed carbohydrate prior 

 to fasting. These data also support the earlier results of Lundbaek and 

 Stevenson/^ who reported that the diaphragm of a carbohydrate-fed rat 

 utilized glucose in vitro at approximately twiite the rate that was noted in 

 the muscle of the fat -fed I'at ^^'hen ])oth tissues were immersed in the glu- 

 cose solution. 



Making use of a somewhat different procedure, Templeton and Ershoff'*^ 

 studied the effect of the foodstuff ingested on the length of survival. When 

 the stress agent employed was thyroxine, it was found that rats fed mar- 

 garine fat or carbohydrate (sucrose) lived appreciably longer than did 

 those which received only the protein, casein. However, no significant 

 differences Avere noted in (-ontrol tests when saline was injected instead of 

 the thyroxine solution. Moreover, when the stress of low^ temperature 

 (2°C.) was employed, the rats fed fat and carbohydrate exhibited a greater 

 I'esistance than did those which consumed only protein. However, this 

 \'ariation in surA'i\-al time was obhterated when the rats were exposed to a 

 temperature of 23 °C. 



Some time is required before the body can adapt itself to high-fat diets 

 when the previous regimen has been rich in carbohydrates and low in fat. 

 According to Geiger, El Rawi, and Catz,^" thyroidectomy does not inter- 

 fere with this adaptation, nor are the adrenal glands recjuired to effect it. 

 It Avas found that adrenalectomized rats utilized dietary fat Avith the same 

 efficiency as did normal animals. Fat-adapted animals have been found 

 to surviA'e longer folloAving adrenalectomy than did animals on a high- 

 carbohj^drate regimen. Finally, it Avas demonstrated by these authors''"" 

 that hypophysectomized animals utilize fat normally, and that adaptation 

 can occur after this operation. 



{6) The Effect of Dietary Fat upon Longevity 



Although fasting animals undoubtedly surA'iA^e longer AA'hen the prefast 

 diet has been composed of fat rather than of carbohydrate or protein, 



" R. C. Gilmore, Jr., and L. T. Samuels, /. Biol. Chem., 181, 813-820 (1949). 

 *^ K. Lundbaek and J. A. F. Stevenson, Federation Proc, 7, 75 (19-48). 

 « H. A. Templeton and B. H. Ershoff, Am. J. Physiol., 15.9, 33-39 (1949). 

 «> E. Geiger, I. I<:i Rawi, and B. Catz, XlXlh Intern. Physiol. Congress, Ahsf., 384-385 

 (1953). 



