18 



Species variation and structural aspects 

 in some pituitary hormones 



CHOH HAO LI 



The Hormone Research Laboratory and the Department of Biochemistry, 

 University of California, Berkeley, California 



The pituitary body is distinguished from all the other endocrine glands by 

 its structural division into three main parts. The posterior lobe, connected 

 with the brain by the infundibulum, is the secretory site of the two peptide 

 hormones, vasopressin and oxytocin. The intermediate lobe, which controls 

 the dispersion of pigment granules, lies between the anterior lobe and the 

 posterior lobe. It is, however, the glandular or anterior lobe that is respon- 

 sible for the physiological dominance exercised by the pituitary over the 

 other glands of internal secretion. Fig. 1 presents a diagrammatic summary 

 of the biological properties of the pituitary hormones. 



Despite the intensive investigations into the various biological functions 

 of the anterior pituitary which have been carried out in recent years, there 

 is as yet no conclusive evidence for attributing the functions of this lobe to 

 any new hormone other than the six already established ;^-2 namely, growth 

 hormone (GH, or somatotropin (STH)), corticotropin (ACTH), thyrotropin 

 (TSH), lactogenic hormone (luteotropin, prolactin), foUicle-stimulating hor- 

 mone (FSH), and interstitial-cell stimulating hormone (ICSH, or luteinizing 

 hormone (LH)). These hormones are protein or peptide in nature, and three 

 of them (TSH, FSH, and ICSH) appear to contain carbohydrates in addi- 

 tion to amino acids. ^ These three carbohydrate-containing hormone pro- 

 teins have not been isolated in pure form and hence no investigations of 

 their structure have been undertaken. 



The isolation, structure and synthesis of the posterior pituitary hormones 

 have recently been accomplished by du Vigneaud and his collaborators.^ 

 This brilhant achievement is well known and shall not be discussed here, 

 except to note that an interesting species difference was observed between 

 pig and beef vasopressins, the former peptide hormone containing lysine 

 instead of the arginine found in the latter. On the other hand, the oxytocin 



