728 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



3. Lipids Present in the Kidney 



Although the perirenal depots represent an important site for the storage 

 of neutral fat, the proportion of this component within the kidney is mini- 

 mal. In the analyses reported by Williams and co-workers 74 on the kid- 

 neys of rats fifteen days and seventy days of age, the total lipid comprised 

 19.62 and 21.59%, respectively, of the dry weight of the tissue. Of this 

 total, neutral fat accounted for only 4.43% in the kidney of the fifteen-day 

 rat and 3.16% in the kidney of the seventy-day animal. More than 85% 

 of the lipid in the kidneys of the older rats was composed of essential lipids 

 which, obviously, must be concerned with the structure of the organ, and 

 hence would be classified as the constant component. The distribution of 

 the essential lipids in the kidneys of the mature rats was as follows : phos- 

 pholipids, 15.19%; cerebrosides, 1.30%; free cholesterol, 1.00%; and 

 cholesterol ester, 0.94%. The phospholipids were composed of cephalin, 

 7.40%, lecithin, 5.96%, and sphingomyelin, 1.83%. Srere et al. 7 demon- 

 strated that cholesterol synthesis normally occurs in rat kidney. 



Variations in the lipid content of the kidney are associated with species. 

 Mottram 176 and Turner 177 called attention to the relatively high level of total 

 lipids in the kidneys of the cat. The total fatty acids were found to average 

 4.9% (based upon moist weight) in the cat kidney, while the figure for beef 

 kidney was only 2%, and that for the human kidney was 1.9%. In a 

 compilation of the composition of human kidneys, made by Cowie and 

 Magee, 178 the average figures for total lipids, recorded in two series of tests 

 on normal individuals, were 2.06 and 1.87% of the moist tissue. 



When one examines the kidney lipids qualitatively, a certain variability, 

 ascribable to species, is apparent. Javillier and associates 179 listed the 

 total phospholipid content in the kidneys of the several species as follows : 

 pigeon, 3.3% (moist weight); frog, 2.9%; rat, 2.9%; guinea pig, 2.8%; 

 and horse, 2.6%. Variations in iodine number have been noted by 

 Turner 177 ; the values for cat kidney were from 53 to 113, while figures of 134 

 and 131 were reported for the fatty acids of beef and human kidneys, 

 respectively. Thannhauser et al. 36 have cited the following figures for the 

 distribution of phospholipids in two normal human kidneys: total phos- 

 pholipid, 8.38% (based upon dry weight); lecithin, 4.34%; cephalin, 



176 V. H. Mottram, J. Physiol, 50, 380-390 (1916). 



177 K. Turner, Biochem. J., 25, 49-56 (1931). 



178 D. M. Cowie and M. C. Magee, Arch. Internal Med., 53, 391-399 (1934). 



179 M. Javillier, A. Cremieu, and H. Hinglais, Bull. soc. chim. biol, 10, 327-337 (1928); 

 also cited by W. R. Bloor, Biochemistry of the Fatty Acids, Reinhold, New York, 1943, p. 

 199. 



