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18] STRUCTURE OF PITUITARY HORMONES 303 



molecules from beef and pig pituitaries manifest no difference with respect 

 to amino acid composition. 



The speculation that the melanocyte-stimulating hormone (MSH, inter- 

 medin) of the intermediate lobe and ACTH might be identical^ -^ has given 

 a new impetus to the studies on the former hormone. This has led to recent 



"Higher Centers" 



Hypotbola/nus 



Small arterial vessel 



Kidney 



Melanocyte-stimulafinq Hormone 

 (MSH Intermedin) 



•^^ Pigment Cel 



Mammary 

 ^^^\ Gland 



Thyrotropin Gonodotropins 



(TSH) (ICSH, FSH) 



Corticotropin 

 (ACTH) 



Prolactin Somatotropin 

 (Luteotropin) (Growth Hormone) 



CO oo (éi> <i X 



Thyroid Testes Ovory Adrsnol Cortex Ovory j "^ 



^ — \ — \ ^ 



Thyroxin Androgens Estrogens Coriicosteroidsl Progesterone 



Aldosterone 



Mammary 

 Gland 



Soft and 

 bony tissue 

 growth, end 



other 

 metobolic 

 processes 



Fig. 1 . A diagrammatical summary of the biological properties of pituitary hormones. 

 CL.= corpus luteum. 



successes in the isolation and structural elucidation of the hormone from 

 both pig and beef pituitary glands.' In this paper, we shall discuss some 

 recent data derived from structural investigations of MSH, the cortico- 

 tropins, and two anterior pituitary hormones (somatotropin and prolactin), 

 especially with regard to species variations. 



I. MELANOCYTE-STIMULATING HORMONE 

 (MSH, INTERMEDIN) 



In 1916, Smith^ and Allen^ independently reported a striking change in the 

 pigmentation of the tadpole following hypophysectomy. According to 

 Smith, ^"-^i the removal of the hypophysis in the tadpole is followed by a 

 decrease in the amount of intracellular melanin as well as in the number 



