LIPIDS PRESENT IN KIDNEY 729 



3.26%; and sphingomyelin, 0.78%. According to Cowie and Magee, 178 

 the average cholesterol values reported for the kidney of different series 

 of normal individuals average 0.293% of moist weight (0.272, 0.250, 

 0.310, 0.340, and 0.293). 



Bloor 23 - 49 made a detailed analysis of the lipids of beef kidney, and ob- 

 tained the following values: total lipids, 2.53% (moist basis); lecithin, 

 0.88%; cephalin, 0.74%; acetone-soluble fraction, 0.90%; and unsaponi- 

 fiable fraction, 0.19%. The total fatty acids had iodine numbers of 109, 

 110, and 82 in the cephalin, lecithin, and acetone-soluble fractions, respec- 

 tively. Moreover, the liquid fatty acids in these fractions were found to 

 be exceedingly highly unsaturated ; the values for iodine numbers found in 

 the liquid fatty acids were 179, 156, and 136, respectively, in the corre- 

 sponding fractions. 



A slight increase in the proportion of total lipids in the kidney occurs 

 with increasing age. However, when one compares the values for the in- 

 crease in essential lipids, it is observed that a 21% greater content is pres- 

 ent in the seventy-day rats than in the fifteen-day animals; in the same 

 period, a 29% decline occurs in the neutral fat fraction, which decreases 

 from 4.43 to 3.16%. The greatest proportional increase occurs in the phos- 

 pholipids (27%), sphingomyelin increasing 93%, cephalin increasing 27%, 

 and the quantity of lecithin being augmented 74 to the extent of 14%. For a 

 further analysis of these changes, see page 573. 



One of the most important factors concerned with the nature of the kid- 

 ney lipids is diet. The kidneys are almost as active as the liver in the in- 

 corporation of ingested fatty acids into the phospholipid. Perlman et al. n 

 found that the maximum level of labeled phospholipid was reached in the 

 kidney about fifteen hours after it was fed, while it required only ten hours 

 to reach the peak in the case of the liver. The phospholipid was retained 

 longer in the kidney than in the liver or intestine. Similar results were 

 reported by Artom et oZ. 180 - 181 On the other hand, the rate of incorporation 

 of radioactive phosphorus into the phospholipid of the kidney is unin- 

 fluenced by the feeding of fat, in contradistinction to the response of the 

 phospholipids in the intestine and liver after fat is administered. 11 Sin- 

 clair, 157 using elaidic acid as a tracer, reported that the time required for a 

 complete turnover of phospholipid in the kidney of the rat is approximately 

 a week, as contrasted with an interval of eighteen hours for the liver. 



180 C. Artom, G. Sarzana, C. Perrier, M. Santangelo, and E. Segre, Arch, internal, 

 physiol, 45, 32-39 (1937). 



181 C. Artom, G. Sarzana, C. Perrier, M. Santangelo, and E. Segre, Nature, 189, 836- 

 837, 1105-1106(1937). 



