314 



CHOH HAO LI 



[18 



III. LACTOGENIC HORMONES (PROLACTINS, 

 LUTEOTROPINS) 



The first indication that a hormone of the anterior pituitary might effect 

 lactation in mammals was given by the experiments of Strieker and Grueter^^ 

 in 1928. Several years later grow^th, to a macroscopically observable extent, 

 of the crop glands of the pigeon after the administration of pituitary extract 

 was reported by Riddle and Braucher;^^ this effect in the bird has been 

 shown by subsequent work to be due to the same factor that elicits lacta- 

 tion in mammals. A number of terms have since been proposed for this factor, 

 including lactogenic hormone, prolactin, galactin, mammotropin and lacto- 

 gen. After the discovery that the hormone is capable of maintaining luteal 

 function in hypophysectomized rats,^* the term luteotropin was also intro- 

 duced. 



Highly purified preparations of prolactin have been obtained from both 

 beef and sheep pituitary glands. ^'^^ Recently a new simplified procedure has 



0.6 



£ 

 in 



(M 

 o 



c 

 a; 

 Q 



~B 

 o 



Q. 



O 



- Solvent system: 2 -Sutanol /0.4 % aqueous DCA 



0.4- 



0.2 



D---0 Sheep.Theoreticol 

 Û--Û SheeqExperimental 

 o — o Beef, Theoretical 

 — Beef, Experimental 



Sheep 

 K=l.58 



Beef 

 K = 2.07 



10 



20 25 30 35 



Tube Number 



Fig. 5. Countercurrent distribution of sheep and beef prolactin at 20°C in the 2-butanol- 

 0-4% aqueous dichloroacetic acid system. 



been described^^ for the isolation of sheep prolactin; the same method has 

 also been employed for the preparation of prolactin in a highly purified 

 form from bovine pituitaries.^' Earlier observations that sheep prolactin can 

 be differentiated from the beef hormone by differences in solubility beha- 

 vior and in tyrosine content,^ have now been confirmed.^' It may be seen 

 in Fig. 5 that the partition coefficient of beef prolactin is higher than that 

 of the sheep hormone in the 2-butanol-0-4% dichloroacetic acid system. 



