774 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



ovary depend upon the stage of pregnancy. Up to the fourteenth to 

 sixteenth days of pregnancy in the rabbit, phospholipid and free cholesterol 

 increased; a maximum rise of as much as 300% was sometimes observed. 

 The variations in cholesterol ester and neutral fat content during this period 

 were found to be negligible. After the pregnancy had progressed to the 

 halfway mark, the concentration of phospholipid and free cholesterol in the 

 ovaries began to decrease, and this decrease continued until, at term, the 

 values were similar to those at the start of pregnancy. On the other hand, 

 the level of cholesterol ester and neutral fat remained high during the last 

 half of pregnancy; in fact, the value for cholesterol ester did not begin to 

 decline until the last day of pregnancy. The author interprets these find- 

 ings as indicative of the fact that the ovary reaches its maximum activity 

 about the middle of pregnancy, after which the activity decreases to the 

 low figure reached at term. Boyd 386 was unable to demonstrate any pat- 

 tern for the changes in cholesterol and phospholipid in the ovaries of the 

 Brazilian guinea pig (Cavia porcellus) during pregnancy, corresponding to 

 that observed in the case of the sow. The phospholipids remained at the 

 control average of 1250 milligram per cent, and free cholesterol at a pro- 

 estrus mean of 300 milligram per cent, during the entire pregnancy. 



The results obtained by Bloor et al. m for the pregnant sow are likewise 

 characteristic for this species. Phospholipid values continue, during the 

 entire course of pregnancy, at the high levels obtained at ovulation. On 

 the other hand, the total cholesterol level remains somewhat lower than 

 the proestrus level, during the whole sequence of pregnancy. A greater 

 decrease apparently occurs in the cholesterol esters than in the free chole- 

 sterol. Hence, the ratio of lecithin : free cholesterol rises to a lesser degree 

 than that of lecithin : ester cholesterol. 



(3) Lipids in the Uterine Mucosa 



Marked structural changes occur in the uterine mucosa which are asso- 

 ciated with the phenomena of estrus, menstruation, implantation of the 

 embryo, pregnancy, and the puerperium. It has been established through 

 the studies of Bouin and Ancel, 387 and especially of Corner and Allen, 388 

 that the progestational proliferation of the uterine mucosa can be traced 

 to the action of a hormone elaborated by the corpus luteum. 



386 E. M. Boyd, J. Biol. Chem., 112, 591-595 (1936). 



387 P. Bouin and P. Ancel, J. physiol. et pathol. gin., 12, 1-16 (1910). 



388 G. W. Coiner and W. M. Allen, Am. J. Physiol, 88, 326-339, 340-346 (1929). 



