LIPIDS PRESENT IN BONE-MARROW 789 



12. Lipids Present in Bone-Marrow 



The phospholipid content of bone-marrow has been shown by Bolle 450 

 to vary within a narrow range in different animals, viz., beef, 0.46%; 

 pig, 0.43%; sheep, 0.40%; dog, 0.83%; and cat, 1.16%. The lecithin 

 content of bone-marrow is a function of the age of the animals, being highest 

 in the young, and decreasing to a minimum value with increasing age. 460-452 

 On the other hand, total lipid was shown by Dietz 452 to increase with ad- 

 vancing age ; there is an inverse relationship between the lipid and the water 

 content in the bone-marrow. The unsaturated fatty acid content has been 

 found to be higher in gelatinous marrow than in the yellow marrow. The 

 saturated acids consist of palmitic and stearic acids, while the main un- 

 saturated acid is oleic ; small amounts of arachidonic acid are also present. 453 



Newlin and McCay 454 have shown that the marrow cavities in the bones 

 of rabbits serve as storage space for mobile supplies of lipids. It was 

 found that the iodine number of the marrow fat reflected that of the diet, 

 especially when the fat stores of the rabbits were first depleted and then 

 flooded with unsaturated lipid. 



13. Lipids Present in the Stomach and Intestine 



Gastric mucosa was shown to contain lecithins, cephalins, and small 

 amounts of cerebrosides. 455 In contradistinction to the intestinal mucosa, 

 in which the lipid composition varies markedly during the absorption of 

 lipids, the mucosae of the stomach walls have a relatively constant composi- 

 tion. This is due to the fact that the stomach is not the site of absorption 

 of lipids, and the lipids do not pass into these cells to the extent that occurs 

 in the intestinal mucosa. However, it should be remembered that In- 

 ouye 456 recorded that fat droplets could be observed in the gastric mucosa of 

 dogs after the administration of olive or mineral oil. 



In the case of intestinal mucosa, the amount of lipid material which can 

 be isolated depends upon whether or not fatty foods have been fed several 

 hours before the tissues are excised. It is well known that neutral fat, 

 phospholipids, cholesterol, and the fat-soluble vitamins become concen- 

 trated i n the mucosal cells following their absorption from the lumen of the 



480 A. Bolle, Biochem. Z., 24, 179-190 (1910). 



461 W. Glikin, Biochem. Z., 4, 235-243 (1907). 



462 A. A. Dietz, J. Biol. Chem., 165, 505-511 (1946). 



463 L. T. Cheng, Z. physiol. Chem., 201, 209-218 (1931). 



454 H. E. Newlin and C. M. McCay, Arch. Biochem., 17, 125-128 (1948). 



455 B. Uhnoo, Z. physiol. Chem., 256, 104-110 (1938). 



456 T. Inouye, Am. J. Physiol, 69, 116-124 (1924). 



