FACTORS ALTERING CONCENTRATION OF BLOOD LIPIDS 405 



ether-soluble substances of the blood and of 50% in the phosphorus level 

 during the ovulation cycle were reported. 291 Higher blood cholesterol 

 values have likewise been noted in hens during the laying period. 292 ' 293 

 Because of the high concentration of cholesterol in the yolk of the egg, it is 

 logical to assume that a mobilization of this substance in the blood for the 

 transport of the sterol to the yolk must precede its deposition in the egg. 



Abrupt changes in the level of blood lipids occur at the onset of laying. 

 Such changes are strikingly demonstrated in the blood lipid pattern of 

 young hens just prior to their first egg-laying period. Lorenz, Entenman, 

 and Chaikoff 294 reported a sudden rise in blood fat to a value of over 300 

 milligram per cent, with a concomitant increase of phospholipids to approxi- 

 mately 1000 milligram per cent. Although the level of blood cholesterol 

 also increased, the rise was much less spectacular. Marked variations in all 

 of the blood lipid constituents occurred during the course of the egg-laying 

 period. It was later shownj^that the hormone, estrone, produced a 100% 

 increase in the blood lipids in immature females within twelve hours; a 

 marked increase in the blood lipids of males was likewise provoked by this 

 hormone. The variations in the blood lipids of hens as affected by egg- 

 laying are shown in Table 1 1 . 



Results substantially similar to those of Lorenz et aZ. 294,295 have been ob- 

 tained by Walker, Taylor, and Russell. 296 These workers reported that 

 laying hens on normal rations had average plasma lipids amounting to 

 1476 milligram per cent. Phospholipid made up 30% of the total, neutral 

 fat, 62%, and cholesterol, 7%. The blood plasma may contain as much 

 as 13% of lipids. Although a slight decrease in blood lipids occurred when 

 the birds were placed on a low-fat diet, no change was noted when a high- 

 fat regimen was used. 



Diethylstilbestrol, which is widely used for stimulating the growth of 

 chickens, has been shown to have a profound effect on lipid metabolism. 

 Stamler and associates 297 reported a hyperlipemia, sustained over fifteen 

 weeks, in chicks into which 25 mg. pellets of diethylstilbestrol had been 

 implanted at the age of five weeks. A simultaneous increase in cholesterol, 



291 O. Riddle and F. H. Burns, Am. J. Physiol, 81, 711-724 (1927). 



292 C. J. Parhon and M. Parhon, Compt. rend. soc. biol., 89, 349-353 (1923). 



293 C. J. Parhon and M. Parhon, Compt. rend. soc. biol, 90, 150-152 (1924). 



294 F. W. Lorenz, C. Entenman, and I. L. Chaikoff, J. Biol Chem., 122, 619-633 

 (1938). 



295 F. W. Lorenz, I. L. Chaikoff, and C. Entenman, J. Biol Chem., 126, 763-769 (1938). 

 298 H. A. Walker, M. W. Taylor, and W. C. Russell, Poultry Sci., 80, 525 (1951). 



297 J. Stamler, C. Bolene, M. Dudley, and E. Levinson, Endocrinology, 46, 375-381 

 (1950). 



