Table 60. — Kidney damage and liver fat in nonfasted rats losing weight on SP 8 HVO diet 



Kidney damage 



Rats 



Rating for kidney damage 1 



Liver fat on 



dry-weight 





Hyalin 



Cystic 



Glomerular 



basis 



to 2.0 hyalin, no cystic or glomerular damage 



Number 

 8 



7 



Score 

 0. 4 

 3. 



Score 

 

 2.4 



Score 

 

 2.3 



Percent 



25. 6 



2.0 hyalin or more, with cystic and glomerular damage.. _ 



18.5 



1 Based on maximum rating of 4. 



Liver fats tended to be high in nonfasted SPPB 

 rats. 



Rats fed other experimental diets.— In 

 table 64 are summarized the data available on the 

 composition of livers from rats fed some of the 

 other experimental diets. The results are chiefly 

 for moribund rats, and interpretation is com- 

 plicated by the variable weight loss of these 

 animals before death. In spite of the wide range 

 of values obtained, some differences were observed 

 that seemed to be related to diet. On the various 

 diets that consisted of the SPE diet with purified 

 supplements, liver fats were generally high and 

 similar to the results with the unsupplemented 

 diet. When the diet contained cholesterol as the 

 supplement, however, liver fat tended to be some- 

 what higher than for the other modifications of 

 SPE diet, in agreement with the results already 

 discussed for microscopic examinations of this 

 organ for fat. 



In the series to determine the influence of kind 

 and/or level of fat, the livers from rats fed SP 16 

 HVO tended to contain a higher percentage of fat 

 than those from rats on SP 8 HVO. Livers were 

 not excessively fatty with any of these diets, and 

 no consistent differences were observed that related 

 to the level or kind of dietary fat. When diets of 

 100 percent whole egg or egg yolk were fed, liver 

 fats tended to be low and protein correspondingly 

 high in comparison with the liver fat of rats fed 

 a diet containing 25 percent whole egg. The 

 results for rats fed 100 percent whole egg and 100 

 percent egg yolk were similar to each other. The 

 results for a small group of littermates showing 

 little or no weight loss on SPE, Y100, and Y97 + 

 salt diets confirmed the finding that liver fat was 

 lower with 100 percent egg yolk than with SPE 

 diet. Supplementation of the 100 percent egg 

 yolk with salt mixture was without influence on 

 liver fat. The livers of Wistar rats fed SP 8 HVO 

 diet were generally low in fat; 18.4 percent was 

 the highest value obtained. The only high liver 

 fat (42 percent) observed in Wistar rats was for a 

 rat 874 days old that reached a maximum weight 

 of 970 grams on SPE diet. 



Discussion. — Liver fats have been reported to 

 be susceptible to many factors, including age, 

 heredity, and diet. Much of the research dealing 

 with liver lipids has been done on relatively 

 j^oung animals, and little information is available 



on the liver lipids of the rat throughout life. 

 Andrew, Shock, Barrows, and Yiengst (11) 

 reported the results of histological examination of 

 the livers from stock animals 1 and 2 years of age. 

 The two groups of rats were very much alike. 

 Vacuolation indicating fat storage was observed 

 occasionally, but no consistent change with age 

 was apparent. Periportal infiltration of lympho- 

 cytes was seen in the connective tissue around the 

 bile ducts, portal vein, and hepatic artery in some 

 of the older rats. From chemical analysis, 

 Yiengst, Barrows, and Shock (191) reported no 

 differences in fat content of the livers from these 

 two groups of rats. Grunt, Berry, and Knisely 

 (80), and Grunt and Knisely (81) reported that 

 old animals have more hepatic fat than have the 

 young ones, and that genetic factors appear to 

 play a significant role in the development of fatty 

 livers in the rat. 



Literature dealing with the many dietary factors 

 that may produce fatty livers has been exten- 

 sively reviewed by Deuel (47). Publications on 

 this subject are numerous, and only a few that seem 

 closely related to the results under consideration 

 in this bulletin will be discussed. 



Blatherwick, Medlar, Bradshaw, and others 

 (31) fed rats diets containing 75 percent dried 

 liver for periods of 30 and 60 days, and obtained 

 livers of high fat and cholesterol content. Fat 

 accumulation was well marked by 28 days. 

 Fractions from liver were fed alone or with various 

 supplements, including lecithin and cholesterol. 

 Marked differences in the fat and cholesterol 

 content of the fivers were noted, but changes in 

 liver fat were not necessarily paralleled by changes 

 in liver cholesterol. Cholesterol, when added to 

 a diet containing a 70 percent alcoholic precipitate 

 of an aqueous extract of liver, resulted in livers of 

 extremely high fat and cholesterol content. 

 Feeding certain fractions containing cholesterol, 

 however, had relatively little effect. The feeding 

 of cooked egg yolks produced livers with increased 

 cholesterol content and, to a less degree, increased 

 fat. More marked increases were observed with 

 cooked whole eggs. 



McCay, Maynard, Sperling, and Osgood (121) 

 reported higher total lipids, cholesterol, and 

 phospholipids in the liver of rats fed dried fiver 

 than in those fed milk proteins. Tfie lipid com- 

 position of the fivers of these animals was about 



73 



