358 



CELLS, TISSUES, AND ORGANISMS 



TABLE I 



The Physicochemical Characteristics of Growth-Hormone Preparations 



from Various Species 

 (From Li, 1958) 



20' w 



in S; DgQ ^ in cm^/sec; V in cc./g.; f/f^, dissymmetry constant; Pj, iso- 



electric point; cystine in residues per mole. 



logically distinct from the growth hormones of other species (Haya- 

 shida and Li, 1959; Read and Bryan, 1960). Bovine growth hormone, a 

 large molecule compared to that of primates, can be hydrolyzed to an 

 extent of about 25 per cent without loss of biological activity, suggest- 

 ing that this activity resides in the center or "core" of the molecule ( Li, 

 1957, 1958). Since bovine and primate growth hormones are equally 

 active in the rat, while only the primate preparations are active in 

 primates, Li has suggested that the rat may degrade the non-primate 

 hormones to their "active cores," while primates do not have this 

 ability, the implication being that the primate molecules closely re- 

 semble the "active cores" of the non-primate preparations. If this hy- 

 pothesis is correct, the administration of bovine, porcine, or ovine "ac- 

 tive core" to primates would elicit the expected physiological effects. 

 This expectation has not yet been realized by unequivocal experimen- 

 tal evidence. Alternatively, the possibility remains that in the course of 

 evolution, the "effector sites" for the growth-hormone molecule have 

 become more selective, and that a highly specific "lock-and-key" inter- 

 action obtains in primates, whereas a less discriminating relationship 

 between the hormone and its receptor are present in the rat, the dog, 

 and the cat. The solution to this problem will provide important in- 

 sight into the mechanism of action of the growth hormone. 



Although the hypophysectomized guinea pig, like the monkey and 

 man, fails to respond to bovine and porcine growth hormone by an ac- 

 celeration of growth (Mitchell et al, 1954; Knobil and Creep, 1959), 



