Effect of Inanition on the Phospholipid Fatty Acids of the Rat.

Abstract

Terroine and Belin 1 have asserted that the lipid component of the élément constant of whole animals and individual tissues represents the phospholipids of normal animals, and that the degree of unsaturation of the fatty acids of the élément constant (i. e., the phospholipid) is an invariable characteristic, quite independent of the type of diet. The latter assertion is quite at variance with the observations of the author. 2

The élément constant of Terroine represents the residual substance of animals which have died of inanition. On the other hand, the data obtained by the author apply solely to the acetone-insoluble lipids of normal, well-fed animals. This distinct difference suggests the possibility that normal animals contain reserve phospholipid which alone is influenced in its composition by the type of diet and which disappears on fasting.

The data in the accompanying table show that in fasting rats the decrease in phospholipid fatty acids is roughly proportional to the decrease in the weight of the animal, or, in other words, the percentage of phospholipid in the whole rat remains relatively constant. Furthermore there is no change in the composition of the phospholipid during fasting, the iodine number of the fatty acids remaining constant.

These facts indicate that the phospholipid of normal animals does not consist of a stable portion, invariable in amount and in composition, and a labile reserve portion. On the contrary these data strengthen the opinion that the phospholipids are vital constituents of the protoplasm, that they are subject to wear and tear, and that the fatty acids of the food are utilized in the process of repair.