Table 52, in which the results are separated on 

 the basis of kidney weight, shows more clearly 

 this relationship between kidney size and composi- 

 tion. The results for kidneys of the same size 

 were similar regardless of age, diet, or weight 

 loss. The percentage of fat in the kidney tended 

 to decrease and the protein to increase with 

 kidney weight. Although total content of both 

 protein and fat tended to increase with kidney 

 size, enlargement of this organ was due in large 

 part to increased protein. Ash content also 

 increased consistently with increasing kidney 

 weight, but no consistent relation between the 

 percentage of ash and kidney size was observed. 

 High ash values were found most frequently in 

 rats fed SPE diet, but values exceeding 6 percent 

 were obtained occasionally in stock and SP 8 

 HVO rats. Calcium deposition in the kidney did 

 not necessarily parallel the percentage of ash in 

 this organ. Determination of ash in the kidney 

 was the least accurate of the measurements made, 

 because of the relatively small samples available 

 for analysis. 



SPM, SPB, and SPPB diets— In table 53 are 

 summarized data for the composition of kidnevs 

 from rats fed SPM, SPB, and SPPB diets. With 

 these diets, there was little evidence that age or 

 diet influenced the composition of the kidneys 

 from rats that were maintaining then weight, 

 except for the low ash in the kidneys of young 

 SPPB rats. The higher content of fat, protein, 

 and ash in rats 400 to 600 days old was a reflection 

 of the larger kidneys in these older animals. In 

 the moribund rats with weight loss over 100 

 grams, the trend for a high percentage of protein 

 and a low percentage of fat in the large kidneys 

 of SPB and SPPB rats was again apparent. The 

 percentage of ash rarely exceeded 6.0 percent 

 and values for rats fed SPB and SPPB diets 



were similar, although calcium deposits were seen 

 more frequently in kidneys from SPB rats. 



Other experimental diets. — In table 54 are 

 summarized protein, fat, and ash data for the 

 kidneys from rats on additional experimental 

 diets. Analyses were not made for kidneys from 

 rats on all of the diets under investigation. 

 Again, the differences observed tended to parallel 

 kidney size. The low percentages of fat in 

 kidneys from rats fed supplemented SPE diets 

 were similar to those found on the unsupple- 

 mented diet, and were characteristic of those 

 observed with large kidneys regardless of diet. 

 The tendency for ash values to be high in the 

 kidneys from rats fed the supplemented SPE 

 diets was comparable to that observed in moribund 

 rats on the unsupplemented diet. 



Wistar rats fed SP 8 HVO and SPE diets.— 

 Kidneys from Wistar rats fed SP 8 HVO diet were 

 similar in composition to those of the same size 

 from BHE rats. Kidneys from Wistar rats fed 

 SPE diet differed from those in moribund BHE 

 rats fed this diet, as might be expected considering 

 the differences in kidney size. The relatively 

 high percentage of fat in the kidneys of Wistar 

 rats fed SPE diet was of questionable significance 

 in view of the limited data available. Ash values 

 were generally low when compared with those 

 found in the kidneys of BHE rats fed SP 8 HVO 

 or SPE diets. 



Summary. — The influence of diet on the com- 

 position of the kidney depended chiefly on its 

 influence on the size of this organ. Enlargement 

 of the kidney was accompanied by an increase 

 in percentage of protein on the dry-weight basis 

 as well as in total protein content, and by a decrease 

 in the percentage of fat. 



High ash values were found most frequently in 

 rats fed SPE diet. Calcium deposition in the 



Table 52. — Protein, fat, and ash in kidneys of different weights from rats fed stock, SP 8 HVO, and SPE 



diets 



Diet and range of kidnev 



Rats 



Average 

 kidney 

 weight 



Water 



Based on dry weight 



Total content 



weights (grams) 



Protein 



Fat 



Ash 



Protein 



Fat 



Ash 



Stock: 



2.00 to 2.99 __ ... . 



X umber 



20 



7 



4 



40 

 5 

 8 

 6 



30 

 10 



7 

 19 



6 



Grams 



1. 65 

 2.74 

 3.74 



1.64 



2. 37 

 4. 19 

 6. 94 



1. 59 

 2.40 



3. 73 

 6. 90 



11. 1 



Percent 

 76.4 

 78. 9 



81. 2 



76. 5 

 76. 8 

 82.6 

 83.3 



76. 7 

 SO. 9 

 80. 1 



82. 5 

 82. 7 



Percent 

 79.6 

 81.7 

 87.5 



79.2 

 80. 2 

 85. 5 

 84.4 



80. 1 

 79.3 

 82. 1 

 85. 2 

 87.0 



Percent 

 13.5 



11. 7 



8.0 



14. 6 



13.7 



9.4 



9. 1 



14.0 



12. 6 

 11. 1 



8.5 

 8. 1 



Percent 



4. 9 



5. 7 

 4.8 



4.7 

 5.2 

 5.6 



4. 5 



5.0 

 4.0 

 4.6 



6. 1 

 5.3 



Mg. 

 316 

 465 

 613 



304 

 442 

 627 

 979 



297 



400 



606 



1027 



1675 



Mg. 

 52 

 67 

 56 



56 



75 



64 



103 



51 



64 



82 



102 



153 



Mg. 

 19 

 33 



3.00 to 4.99 ._ 



34 



SP 8 HVO: 



Kidnev less than 2.00 



2.00 to 2.99 .. 



3.00 to 4.99 



18 

 29 

 41 



5.00to9.99 



53 



SPE: 



Kidnev less than 2.00 

 2.00 to 2.99 



3.00 to 4.99 



19 

 21 

 34 



5.00 to 9.99 



72 



10.0 and over 



96 



64 



