THE GROWTH-PROMOTING HORMONE 



crude alkaline extract has been attempted by a number of 

 methods. Sodium sulphate can be used to salt out an ex- 

 tract which is less crude (Teel). Several adsorbents (norit, 

 A1(0H)3, and Lloyd's reagent) have been used without suc- 

 cess; Collip and others, however, reported that Ca.^{F0^)2, 

 under proper conditions, adsorbed the hormone and that the 

 elution of the hormone from the adsorbent could be subse- 

 quently accomplished. By adjusting the hydrogen-ion con- 

 centration either inert substances or the crude hormone may 

 be partially separated from a solution. 



Evans, Meyer, and Simpson (1933) described in great de- 

 tail a number of attempts to purify the growth-promoting 

 hormone such as by the use of phosphotungstic acid, flavianic 

 acid, trichloracetic acid, adjustment of the hydrogen-ion con- 

 centration (what they term "iso-electric precipitation"), etc. 

 The physico-chemical changes involved in many of their 

 methods appear to be very complex; consequently, even 

 slight changes in technique might markedly alter the results. 

 They point out that growth-promoting extracts may be ex- 

 tremely labile under certain conditions. 



Little that is significant is known about the properties of 

 growth-promoting extracts. They appear not to dialyze (col- 

 lodion or other membranes) and to be heat-labile. Some ex- 

 tracts in a dilute aqueous solution of alkali will withstand a 

 temperature of 60° C. (but not 80°) for 15 minutes. Others 

 appear to be inactivated at lower temperatures. 



How potent and how specific in their growth-promoting 

 eflFects are various extracts? As to potency, the following re- 

 marks can be made. The preparation of van Dyke and 

 Wallen-Lawrence, in a dose of 0.35 cc. per kg. rat or about 

 0.09 cc. for a female rat of 250 g. per day for 3 days, produced 

 a total increase in weight amounting to 3 per cent. The total 

 dose, 0.27 cc, contained about 2.7 mg. of total solids in part 

 made up of protein (0.88 mg. computed from the total N, 

 0.1 4 mg.); probably most of the solids were salts. Evans, 



[107] 



