Serum protein changes during differentiation 

 EARL FRIEDEN 



Department of Chemistry, Florida State University, 

 Tallahassee, Florida, U.S.A. 



Biochemists have long cherished the hope that the phylogenetic classifica- 

 tion of animals, based essentially on morphology, would find a correspond- 

 ing chemical expression of evolutionary differences between animals. The 

 discussion here today has also served to emphasize the relation between 

 species specificity and protein structure. I now wish to present some recent 

 data which illustrate the variation in proteins that occur during develop- 

 mental changes in a given species. 



For some years we have been studying the chemical changes that are 

 associated with amphibian metamorphosis.^ Recently, in collaboration with 

 Albert Herner, Lloyd Fish, and Mrs E. J. Casson Lewis, we have observed 

 significant alterations in serum proteins during normal and induced meta- 

 morphosis.^ Marked changes in both the amount and the distribution of 

 the serum proteins were noted. The distribution of the serum proteins was 

 estimated from paper electrophoresis studies of serum obtained from freshly 

 clotted tadpole and frog blood. 



As shown in Table 1, the Florida swamp frog has virtually no detectable 

 protein in the electrophoretic fraction corresponding to serum albumin. As 

 metamorphosis proceeds, the albumin fraction appears and increases until 

 a normal complement of 45% is observed for the frog of this species. The 

 common bullfrog tadpole has a small fraction of serum albumin which also 

 increases until the albumin is about one-half of the total serum protein. 

 The very young bullfrog and the adult bullfrog possess identical propor- 

 tions of serum albumin. In early tadpoles of both of these species, the 

 albumin fraction can be appreciably increased by the administration of 

 thyroid hormone. The non-albumin fraction of tadpole serum protein seems 

 to be predominantly globulin in character. 



The implications of these observations for comparative biochemistry are 

 too numerous and lengthy to be fully discussed here and will be presented else- 

 where. ^ We think that it is not unlikely that the tadpole-frog system is 

 reflecting a serum protein alteration typical of the change from aquatic to 

 terrestrial forms. ^ 



Certain subtle changes also occur in the hemoglobins of the metamor- 

 phosing bullfrog tadpole as reported previously by McCutcheon^ and by 



