min), FC (fast moving) or Rho (rapid). Azerod, 

 Lewin, and Ghata (16) obtained evidence of two 

 prealbumin protein fractions in normal human 

 serum, an electropkoretically homogeneous frac- 

 tion migrating slightly faster than albumin and a 

 heterogeneous fraction spread over a large area 

 in front of the albumin. A change in the mobility 

 of the blood proteins and the presence of a rapidly 

 moving prealbumin fraction as the result of the 

 administration of heparin to lipemic individuals 

 was noted by Nikkila (139), Lever, Smith, and 

 Hurley (113, 114), and Herbst and Hurley (87). 



The influence of heparin on the blood proteins 

 appears to be attributable to the liberation of a 

 lipoprotein lipase (107) into the blood and to the 

 production of more rapidly migrating fractions 

 due to the association of the fatty acids with some 

 of the blood proteins (75). Interest in this 

 heparin clearing reaction has been evidenced 

 because of its possible role in fat transport. The 

 concentration of this clearing factor in blood 

 serum is normally low, and the physiological im- 

 portance of the reaction has not been definitely 

 established. Many of the investigations have 

 dealt with measurements of enzyme activity as 

 determined by clearing of lipemic sera or liberation 

 of free fatty acids, and have not included electro- 

 phoretic measurements of the blood proteins. The 

 present status of our knowledge of clearing factor 

 has been reviewed by Robinson (159) and 

 Engelberg (57). _ 



The data available from electrophoretic studies 

 of sera from BHE rats have provided no informa- 

 tion concerning the chemical nature of these fast- 

 moving components and no proof that these com- 

 ponents were the same as those resulting from the 

 administration of heparin. There seemed to be 

 considerable indirect evidence linking high level 

 of this component to the lipid metabolism of these 

 rats. Elevated serum cholesterol values were 

 obtained for the majority of the rats with high 



levels of PA in their sera. The lipemic sera that 

 were encountered frequently, even after the usual 

 17-hour fast, were associated generally with high 

 levels of one or more fast-moving components. 

 Rosenman and Smith (164) indicated a possible 

 causal relationship between deficiency of albumin 

 and increased lipid content of nephrotic plasma. 

 Whether or not the albumin content of the blood 

 of BHE rats was a factor in the results obtained 

 could not be determined from the data available. 

 The relative values for the various protein com- 

 ponents in serum protein provide no information 

 on the actual concentration of these fractions in 

 the serum. Further investigations are underway 

 to determine the possible physiological significance 

 of PA and the relation of these components to 

 lipid metabolism. 



Summary. — -With the BHE strain of rats, age 

 and diet were found to influence the relative 

 amount of the various protein components. Of 

 particular interest was the frequent occurrence of 

 a component or components moving more rapidly 

 than albumin (PA). 



In stock rats 300 days or younger, there was no 

 evidence of the fast-moving component and, except 

 in the sera of a few moribund rats, the amounts of 

 PA were relatively small even in the older animals. 

 PA was present in the sera of some of the younger 

 rats fed the semipurified diet or SPM, SPB, or 

 SPPB diets, with a tendency for high levels in the 

 older rats. On SPE diet, levels of PA tended to 

 be high at all ages, with the largest proportion of 

 rats with serum containing this component in the 

 300- to 399-day-old group. 



Small amounts of PA were observed in approxi- 

 mately 50 percent of the rats with normal kidneys 

 and serum cholesterol levels, irrespective of the 

 experimental diet. When serum levels of PA were 

 high, they were often associated with enlarged 

 and damaged kidneys and with high cholesterol 

 levels. 



General Summary and Implications for Future Research 



Results are reported from long-term studies 

 with male rats dealing with the influence of diet 

 on length of life and changes that occur with age 

 in blood serum and in livers, kidneys, adrenals, 

 and thyroids. The diets investigated were mod- 

 ifications of a relatively simple semipurified diet. 

 Egg, beef, milk, or peanut butter were substituted 

 for 20 to 25 percent of the semipurified diet in one 

 series of experimental diets; the kind and level 

 of fat in the semipurified diet was varied in the 

 second series of diets. The fats included a 

 hydrogenated vegetable oil, lard, and butter, and 

 the levels used were 8 and 16 percent. For com- 

 parative purposes, data were obtained for animals 



721-631—64- 



raised on the diet routinely used for maintaining 

 the laboratory stock colony. Results showing the 

 influence of fasting and of weight loss before 

 sacrifice have also been included. Most of the 

 data reported are for BHE rats, a mixed strain 

 of animals bred in our stock colony, but also 

 included are the results of feeding a group of 

 Wistar rats the semipurified diet and the diet 

 containing 25 percent cooked dried egg. 



The animals grew well on all of the experimental 

 diets and generally attained a maximum weight 

 greater than that observed with rats on the stock 

 diet. During the period of early growth, rats 

 fed the diets containing egg, milk, beef, or peanut 



91 



