THE GONADOTROPIC HORMONES 



tropic potency (rabbit-ovulation test) of the ewe's pituitary 

 during this animal's oestrous cycle. Schmidt (1937) found 

 that, as tested in the immature female guinea pig, the gonad- 

 otropic potency of the adult female's pituitary is least dur- 

 ing oestrus and greatest during pro-oestrus. Also she made 

 a similar study of the pituitary of female adults receiving a 

 minimal sterilizing dose of X-rays. The gonadotropic po- 

 tency of the pituitary did not always correspond to the nor- 

 mal sexual cycle as judged by the vagina. For example, the 

 pituitary, although removed from an animal in prolonged 

 oestrus, might contain much gonadotropic hormone. The 

 metaboHsm of the pars glandularis of the rat in different 

 phases of reproductive activity has been investigated by Vic- 

 tor and Andersen (1936) and Andersen, Prest, and Victor 

 (1937). Their results can be summarized as follows: 



Oxygen-consumption : 



Pro-oestrus > oestrus > dioestrus or spayed 



Parturition > lactation > pregnancy 

 Aerobic glycolysis: 



Spayed > dioestrus 

 Anaerobic glycolysis: 



Pro-oestrus or oestrus > dioestrus or spayed 



The highest oxygen-consumption was found in parturient 

 animals, the lowest in spayed animals. It was about the 

 same in lactating rats and rats in pro-oestrus. There were 

 no significant differences in the aerobic and anaerobic glycoly- 

 sis of pregnant, parturient, and lactating rats. 



The effect of pregnancy on the assay of gonadotropic hor- 

 mones has been investigated by Rowlands (1935), who used 

 rabbits and expressed dosages in terms of the amount of ex- 

 tract causing ovulation in 50 per cent of each group. Table i 

 is a summary of Rowlands' results. 



These observations suggest the following conclusions: (i) 

 The "ovulating dose" of a gonadotropic hormone is higher 

 in pregnancy than in oestrus. (2) Pituitary extracts, but not 

 prolan, may vary enormously, depending upon their source, 



[69] 



