Table 20. — Liver fat determined microscopically for rats fed SPM, SPB, and SPPB diets 



Weight status, diet, and age of rats (days) 



Rats 



Average 

 age 



Average 



weight 



loss 



Histological rating 

 of liver fat 





Small 

 vacuoles 



Large 

 vacuoles 



Rats maintaining weight: 

 SPM: 



Less than 400 . _ 



Number 



16 



5 



16 

 6 



15 

 9 



17 

 15 

 29 



14 

 17 

 13 



Days 

 240 

 497 



241 



489 



232 

 516 



449 

 446 

 429 



624 

 572 

 502 



Grams 

 

 





 





 



47 

 51 

 52 



175 

 175 

 177 



Score 

 0.2 

 . 6 





 







.8 



. 1 

 

 .3 



. 5 

 . 1 

 



Score 

 0. 1 



400 to 599 _- _ - - . - 



. 2 



SPB: 



Less than 400- - . . ______ 



. 1 



400 to 599_ 



. 5 



SPPB: 



Less than 400 _ ______ 







400 to 599 _ . ___ __ _ _ .__ 



. 9 



Rats losing less than 100 grams: 



SPM 



. 1 



SPB 



. 1 



SPPB 



. 3 



Rats losing more than 100 grams: 



SPM 



. 8 



SPB 



. 1 



SPPB 











added. There was no evidence that the presence 

 of fat droplets in the liver was related to the kind 

 or level of fat in the diet. There was a tendency 

 to fatty livers with all of the diets containing 

 whole egg or egg yolk, although the livers of rats 

 consuming 100 percent egg appeared to contain 

 less fat than those of rats fed the diet containing 

 25 percent egg (SPE). Although the addition of 

 salt mixture to diet Y100 seemed to prevent the 

 occurrence of extensive kidney damage, the liver 

 fat of the animals fed this diet, with or without 

 the mineral supplement, seemed to be similar. 

 Relatively little fat was apparent microscopically 

 in the livers of rats changed from stock to SPE 

 diet at 250 days; when the reverse procedure was 

 used (SPE to stock at 250 days), liver fat re- 

 sembled that seen in animals continued on SPE 

 diet throughout life. 



Although there was a tendency for more fat in 

 the livers of Wistar rats fed SPE diet than for 

 this same strain of rat fed SP 8 HVO diet, the 

 amount of fat appeared to be less than that 

 generally found in BHE rats fed SPE diet. 



Quantitative data concerning fat in the liver as 

 influenced by diet and age are provided by chemi- 

 cal analyses and are reported in a later section of 

 this publication in which the problem of liver fat 

 is considered in greater detail. 



Kidney and liver weight 



Kidney weight of animals maintaining 

 weight on stock, sp 8 hvo, and spe diets.— 

 In table 22 are summarized for different age 

 groups the weight of the kidneys from rats that 

 were consuming stock, SP 8 HVO, or SPE diets 

 and that were maintaining weight at the time of 

 sacrifice. Included are data comparing the weights 



of kidneys from rats that were fasted for 17 hours 

 and bled by cardiac puncture, with those from 

 rats that were neither fasted nor bled at the time 

 of sacrifice. 



On stock diet, kidney size of fasted rats appar- 

 ently varied little with age. The average kidney 

 weight of 1.56 grams represented 0.36 percent of 

 the body weight. The largest kidney obtained 

 weighed 2.10 grams, and only 3 of the 38 rats had 

 kidneys exceeding 2.0 grams in weight. The re- 

 lation between kidney and body weight was rela- 

 tively constant for all age groups. In contrast, 

 kidneys from nonfasted rats tended to increase in 

 size with age and to represent an increase in rela- 

 tion to body weight from 0.36 percent in young 

 rats to 0.47 percent in rats over 600 days old. The 

 kidneys from these rats tended to be larger than 

 those from fasted rats of comparable age, exceed- 

 ing 2.0 grams in 9 of the 11 rats that were over 

 600 days old. 



On the semipurified diet, the kidneys from 200- 

 to 499-day-old fasted rats were similar in weight 

 to those from rats fed the stock diet but were some- 

 what larger in the older rats. Kidneys exceeding 

 2.0 grams in weight were obtained from 35 percent 

 of the rats that were between 500 and 600 days 

 old. In relation to body weight, the kidneys were 

 significantly smaller (P < 0.01) than those from 

 rats fed the stock diet. Data for nonfasted rats 

 fed SP 8 HVO diet were limited to animals less 

 than 400 days old, but kidneys tended to be large 

 even in these young rats. Kidney weights for rats 

 300 to 399 days old were similar to those for rats 

 under 200 days old, in spite of the increase in body 

 weight of approximately 100 grams. 



On SPE diet, the kidneys of fasted rats tended 

 to be larger than those from comparable stock or 



37 



