416 V. BLOOD LIPIDS 



decrease in plasma cholesterol occurs in rats fed over a period of weeks on a 

 fat-free diet, the cholesterol level in the liver and adrenal glands is increased 

 markedly above the normal value. In contradistinction to this, rats fed 

 on a 12.5% fat diet presented normal levels of plasma cholesterol, together 

 with a normal cholesterol content in the liver and adrenals. Thus, while 

 the cholesterol level in the livers of animals on the high-fat diet was ap- 

 proximately 2 milligram per cent, that found for the rats on the fat-free 

 diet varied from 3 to over 6 milligram per cent. It is thus evident that 

 plasma cholesterol may not mirror the storage and the concomitant deposi- 

 tion of this lipid occurring in the liver. 



(b) Postabsorptive Effects of the Ingestion of Fat. In addition to the im- 

 mediate effects of fat ingestion on the level of various components of the 

 serum lipids, there may likewise be a prolonged effect, which persists 

 over several days, on the levels of their constituents. Bloor 364 found that 

 the feeding of moderately high fat diets to dogs over considerable periods of 

 time resulted in increased amounts of serum phospholipids, but that the 

 neutral fat and cholesterol in the serum were less affected. Bloor 227 

 later reported that the phospholipid level of dogs was elevated over several 

 days following a single large feeding of fat or carbohydrate (making up 

 more than 50% of the calories) ; protein, however, did not provoke this 

 augmentation in blood phospholipid. Hansen and his collaborators 365 

 likewise found that the feeding of fatty diets increased the blood lipids of 

 dogs ; in their experiments, all fractions of the blood were affected. Enten- 

 man and Chaikoff 366 were able to demonstrate that, after one feeding, 

 an increase in blood cholesterol occurred, while the fatty acid and the 

 phospholipid in the serum were only slightly increased. On the other 

 hand, Flock et al. w reported that the postprandial level of blood lipids 

 was increased in their dogs only when phospholipids were fed concomitantly 

 with neutral fat ; the higher percentages of neutral fat resulted in a greater 

 response. Bloor 364 noted that the rabbit is much more sensitive to changes 

 in dietary fat, as reflected in the level of blood lipids, than is the dog or man. 



According to a 'number of reports of tests on human subjects, a relation- 

 ship appears to obtain between the dietary fat and the level of serum li- 

 pids. Thus, McQuarrie and associates 368 reported a marked increase in 



364 W. R. Bloor, /. Biol. Chem., 95, 633-644 (1932). 



366 A. E. Hansen, W. R. Wilson, and H. H. Williams, J. Biol. Chem., 114, 209-222 

 (1936). 



366 C. Entenman and I. L. Chaikoff, J. Biol. Chem., 142, 129-139 (1942). 



367 E. V. Flock, W. C. Corwin, and J. L. Bollman, Am. J. Physiol, 123, 558-565 

 (1938). 



368 1. McQuarrie, C. Husted, and W. R. Bloor, J. Clin. Invest., 12, 255-265 (1933). 



