GESTATION 



985 



and higher of HCG following the injection 

 of HCG, Johnson, Albert and Wilson (1950) 

 found an excretion of 5.8 per cent in preg- 

 nant women during the immediate post- 

 partum period. Zondek and Sulman (1945) 

 reported a 5 to 10 i)er cent elimination of 

 HCG in the urine of animals. Thus Brad- 

 bury and Brown felt that there is relatively 

 little destruction or utilization of the hor- 

 mone in the body; Wilson, Albert and 

 Randall ( 1949) believed that 94 per cent of 

 the circulating hormone is affected by extra- 

 renal factors and that the fluctuating char- 

 acter of hormonal level in serum or urine 

 depends entirely on changes in rate of hor- 

 mone production. 



An analysis of the distribution of chorionic 

 gonadotrophin in the mother and fetus led 

 Bruner (1951) to conclude that the ratio of 

 maternal blood to urinary gonadotrophin is 

 not constant although the ratio of gonado- 

 trophin in the chorion to maternal blood is 

 constant. Consequently, she concluded that 

 the concentration of gonadotrophin in the 

 urine does not depend entirely on the rate of 

 production of the hormone and that the 



method of gonadotrophin elimination 

 changes during pregnancy. She also pointed 

 out that a significant amount of chorionic 

 gonadotrophin is found in the fetus and that 

 this is due to the fact that, although the 

 chorion releases the hormone into the mater- 

 nal blood, secondarily some of it passes the 

 placental barrier and enters the fetal sys- 

 tem across the wall of the chorionic vesicle. 



2. Equine Goyiadotrophin (PAIS) 



The presence of a gonadotrophin in the 

 blood of the pregnant mare was first de- 

 scribed by Cole and Hart in 1930. The hor- 

 mone appears in the blood about the 40th 

 day of pregnancy and increases rapidly to a 

 concentration of 50 to 100 rat units (R.U.) 

 per ml. by the 60th day of pregnancy (Cole 

 and Saunders, 1935). This concentration is 

 maintained for approximately 40 to 65 days. 

 By day 170 it has fallen to a nondetectable 

 level (Fig. 16.22). 



Catchpole and Lyons (1934) suggested 

 that the placenta is the source of the gonado- 

 trophin and indicated that the chorionic 

 epithelium is the probable source. Cole and 



leae/7(f 



• Co/7ce/7irct/o/? of oes^r/y?. 



— /re/7<y of ///tf co/7cs/7^rot/o/f of oasin. 



/PO /ss 



//s ^oo ^^s ^so ^7s joo ses 



^^ayj prfyrjo/?^ 



Fk;. 16.22. Tlie concentration of i)rognant mare's serum in the blood of the mare throug 

 out pregnancy. (From H. H. Cole and F. J. Saunders, Endocrinology. 19, 199, 1935.) 



