Table 14. — Kidney damage determined microscopically for rats maintaining weight at different ages on 



stock, SP 8 HVO, and SPE diets 



Diet and age of rats 



Rats 



Gross 

 rating 



Histological rating 



Kidneys with — 



(days) 



Hyalin 



Cystic 



Glomerular 



Hyalin 



Cystic 



Glomerular 



Stock: 



Less than 200 



200 to 299... 



Number 

 19 

 18 

 11 

 10 

 11 

 16 



5 

 12 



8 

 7 

 9 



5 

 23 



12 



14 



9 



Score 

 

 . 2 

 .6 

 . 6 

 .8 

 1.0 



. 4 

 .3 

 . 2 



. 4 

 . 8 



. 2 

 . 8 



1. 6 

 1.5 



2. 2 



Score 







. 1 



. 3 



. 7 



1.0 



1. 2 



. 4 

 . 2 

 . 4 

 . 4 



.7 







1. 1 

 1.6 

 1. 1 

 1.8 



Score 









 . 1 

 . 1 

 . 4 

 . 4 





 

 

 

 .3 





 . 1 

 . 4 

 . 1 

 .3 



Score 









 . 1 

 . 2 

 . 5 

 . 4 





 

 

 

 . 3 





 .04 

 . 1 



2 



'.3 



Percent 

 

 11 

 18 

 50 

 64 

 81 



20 

 17 

 38 

 29 

 56 







78 



92 



64 



100 



Percent 











9 



10 



27 



19 





 

 

 

 11 











33 



14 

 33 



Percent 





 



300 to 399.. . ._ 



9 



400 to 499.. . .. . 



10 



500 to 599 . 



18 



600 and over. 



31 



SP 8 HVO: 



Less than 200. . 

 200 to 299 . 





 



300 to 399.. . 







400 to 499 ... 







500 to 599.. .. 



11 



SPE: 



Less than 200 



200 to 299.. 







4 



300 to 399 . _ 



8 



400 to 499. 



21 



500 to 599 . 



33 







In general, the kidneys of rats under 200 days 

 of age were normal on all three diets. On stock 

 or SP 8 HVO diet extensive degenerative changes 

 in the kidney were rarely seen. A gradual 

 increase occurred with age in the number of rats 

 fed stock or SP 8 HVO diets, with kidneys showing 

 the presence of eosinophilic albuminous material 

 or hyalin casts. Kidneys from 81 percent of the 

 rats fed the stock diet that were over 600 days old 

 had a hyalin rating of 1 or more, although one of 

 the oldest rats (916 days) had a kidney that was 

 apparently normal. Cystic or glomerular damage 

 was found occasionally and was seen more often 

 in the kidneys from rats fed the stock diet than 

 from those fed SP 8 HVO diet. 



On SPE diet the results were in marked con- 

 trast. Of those animals that were fed this diet 

 and were more than 200 days old, relatively few 

 had normal kidneys. Kidneys with hyalin ratings 

 of 2 or 3 were observed even in rats 200 to 300 

 days old. Cystic or glomerular damage was 

 occasionally seen but was generally slight. 



Calcium deposits were not observed in the 

 kidneys of rats that were maintaining weight on 

 any one of these three diets. 



PvATS LOSING WEIGHT ON STOCK, SP 8 HVO, 



and SPE diets. — Both age and weight loss were 

 found to influence the type and extent of kidney 

 damage observed, and the data summarized in 

 table 15 have been separated accordingly. 



For rats fed the stock diet and with weight loss 

 less than 100 grams, little damage was observed in 

 the kidneys from the few animals that were less 

 than 700 days old; extensive degenerative changes 

 were observed in kidneys from rats over 700 days 

 old, with 40 to 75 percent of the kidneys showing 

 cystic and glomerular damage as well as hyalin 



casts. When weight loss exceeded 100 grams, 86 

 percent of the kidneys showed all three types of 

 damage and the extent of the damage observed 

 bore no relation to age. When cystic damage was 

 large, there was a tendency for a reduction in 

 hyalin casts. Fibrosis was generally apparent 

 when all three types of damage were evident. 

 Calcium was present in only one of these kidneys. 



Animals fed the semipurified diet with weight 

 loss less than 100 grams presented a somewhat 

 different picture from that of animals fed the stock 

 diet. The most extensive damage was found in 

 kidneys from the small group of rats between 500 

 and 600 days of age; kidneys from animals sur- 

 viving over 600 days tended to show progressively 

 less damage with increasing age. Relatively little 

 cystic or glomerular damage was observed. When 

 weight loss exceeded 100 grams, only 2 of the 29 

 kidneys from rats 400 days of age or older were 

 normal; no consistent relation between age and 

 extent of damage was observed. Cystic and glo- 

 merular damage was found in 65 percent of these 

 kidneys, a marked increase over that seen in rats 

 losing less weight but somewhat lower than that 

 found for comparable groups of rats fed the stock 

 diet. Calcium deposits were found in the kidneys 

 of 41 percent of these animals and appeared to be 

 the heaviest between 400 and 600 days of age. 

 Calcium was apparent only when all three types of 

 damage were present. The data for fasted rats 

 were too few to determine whether or not the 

 nutritional state of the rat at the time of sacrifice 

 was a factor in determining the presence of calcium 

 in the kidneys of these rats. 



On SPE diet, relatively few normal kidneys were 

 observed, regardless of age or weight loss. For 

 rats under 400 days of age and losing less than 100 



30 



