THE PITUITARY BODY 



Ian in the pregnant individual is still undecided, it more likely 

 is secreted by the placenta than by the pituitary. (The cru- 

 cial experiment of hypophysectomizing a pregnant woman 

 and subsequently determining the distribution and excretion 

 of prolan is not likely to be performed.) Therefore, although 

 the gonadotropic substance secured from urine of spayed or 

 other non-pregnant individuals may be called "prolan A," it 

 is not necessarily identical with or related to the prolan of 

 pregnancy. Second, a prolan causing "B," but no other ef- 

 fects, has been secured only by Brindeau, Hinglais, and 

 Hinglais (1934). They give no worth-while description of 

 their method of preparation. Moreover, they postulate a 

 third "preluteinizing" hormone which must be present before 

 "prolan B" can bring about luteinization.^ 



The presumed separation of follicle-maturing and luteiniz- 

 ing fractions from gonadotropic extracts of the anterior pitui- 

 tary (see chap, iv) provides an analogy but no direct support 

 for the belief that prolan is composed of at least two gonado- 

 tropic substances.'^ Small doses of prolan tend to cause only 

 follicular growth; larger doses tend to cause hemorrhage into 

 follicles and the formation of corpora lutea with or without 

 preceding ovulation. Some interpret this rough relationship 

 between dose and effect as indicating the presence of only one 

 hormone. However, it might with equal justice be inter- 

 preted as indicating a different and steeper "curve of re- 

 sponse" to "prolan A" than to "prolan B" (see Fig. 40). 

 Again, different samples of prolan differ in the relative doses 

 required to cause follicular maturation (or oestrus) and lute- 

 inization. For example, the dose causing oestrus in immature 

 rats may vary from 9 to 55 per cent of the dose causing lute- 

 inization if different samples of prolan are examined (Coester, 



^ Also see Lipschiitz (1933, 1935), and chap. iv. 



^ Prolan from pregnancy-urine or placenta could not be separated into "A" and 

 "B" fractions by methods which were used in separating the follicle-maturing and 

 luteinizing fractions of anterior pituitary extracts (Fevold, Hisaw, Hellbaum and 

 Hertz, 1933). 



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