THE GONADOTROPIC HORMONES 



considered to be due to the luteinizing hormone liberated by 

 the pituitary in situ and to some extent was related to the 

 size of the oestrin dose.-*^ No such increased effect of follicle- 

 stimulating hormone after oestrin occurred in hypophysec- 

 tomized rats. In normal animals, the injection of prolan after 

 oestrin produced no ovarian hypertrophy greater than after 

 prolan alone. If prolan be considered a luteinizing hormone, 

 this result indicates that oestrin does not facilitate the secre- 

 tion of a synergizing, follicle-stimulating hormone. If oestrin 

 was injected for 8 days, the ovarian response to pituitary 

 follicle-stimulating hormone or prolan was reduced in nor- 

 mal but not in hypophysectomized rats, indicating that this 

 antagonistic effect is on the pituitary, by which some gonado- 

 tropic hormone is secreted even in immature animals, and 

 not on the ovary, x^ll these results suggest the following con- 

 clusions: (i) oestrin in small doses increases the rate of secre- 

 tion of luteinizing, but not of follicle-stimulating, hormone; 

 (2) larger doses of oestrin (8-day injection period) diminish 

 the rate of secretion of both gonadotropic hormones; and (3) 

 oestrin appears to have no effect on the ovary. ^"^ 



Leonard's results (1937) led to a different interpretation as 

 far as conclusion (2) is concerned; however, he used a differ- 

 ent method. He estimated the quantity of follicle-stimulating 

 or luteinizing hormone in the pituitary of the rat receiving 

 oestrin by determining the effect of a maximum dose of prolan 

 (50 rat-units) or menopausal urine (equivalent to 100 cc.) and 

 comparing these effects (i) with those of pituitary tissue from 

 control animals and animals receiving oestrin and (2) with 

 the effects of pituitary tissue in addition to prolan or extract 

 of menopausal urine. The degree of augmentation of the 

 effect of prolan on the ovary was taken as a measure of the 

 quantity of follicle-stimulating hormone present in the ad- 



3^ The maximum effect apparently was produced by 0.5 R.U. of oestrin. 



^' Earlier work had indicated that ovarian regression due to a "sex hormone" 

 is an indirect result of diminished pituitary function. See, however, the results of 

 Robson in the rabbit discussed on pp. 86-87. 



[85] 



