THE GONADOTROPIC HORMONES 



oestrogen in causing persistence of corpora lutea. The other 

 evidence available indicates that the secretion of luteinizing 

 hormone by the pars glandularis is responsible for the appear- 

 ance of corpora lutea, when these follow the injection of an 

 oestrogen. According to Robson, oestrone (107 daily) or 

 oestradiol (57 daily) maintains the structure and function of 

 pseudopregnant corpora lutea of hypophysectomized rabbits 

 for as long as 13 days/^ As in hypophysectomized rabbits re- 

 ceiving no oestrogen, the ovary of these animals did not re- 

 spond to gonadotropic hormone. The observations of West- 

 man and Jacobsohn (1937) are fully in agreement with those 

 of Robson. 



Late in pregnancy in the rat, the administration of 0.5 mg. 

 of oestrone daily increases the duration of pregnancy to about 

 24-26 days (Selye, CoUip, and Thomson, 1935). The authors 

 concluded that this treatment prolongs the life of the corpora 

 lutea, giving rise to interference with parturition and fetal 

 death. Pincus and Kirsch (1936) studied the effect of oestro- 

 gens on ovulation and implantation in the rabbit. As much 

 as 3,000 rat-units of oestrone, given before mating, did not 

 prevent ovulation. The administration of oestrone during 

 the 3-6 days after coitus caused a considerable reduction in 

 the number of implantation sites. The authors concluded 

 that ova were killed in the early blastocyst stage but that 

 cleavage was not affected. Some oestrogens were more harm- 

 ful than others. Implanted ova, like the fetuses into which 

 they developed, were normal. The experiments of Courrier 

 and Gros (1935) in the cat indicated that "folliculin" pre- 

 vents nidation in the cat if a total dose of 500-1,000 rat-units 

 be administered on the 5-18 days following coitus. Abortion 

 was caused by 1,000 rat-units during the 38-43 days, al- 

 though other doses at other times might not have this effect. 



Experiments in parabiotic rats indicate that oestrone inter- 

 feres with the liberation of gonadotropic hormone by the 

 gonadectomized partner. Meyer and Hertz (1937) injected 



■t^ In one experiment i mg. of testosterone daily was without effect. 



[87] 



