i86 



Pituitary Gonadotrophins 



tatively and qualitatively similar in biological activity but quite different 

 chemically (see table i). 



The follicle-stimulating factor has not yet been obtained in pure form. 

 Active fractions are soluble in water and half saturated ammonium sulfate; 

 they contain almost twice as much carbohydrate as the ICSH."'^" Comparison 

 of FSH from different species has to be postponed until final purification will 

 have been achieved. At the present it can only be stated that the best sheep 

 FSH is considerably more active and appears to be more stable than is pig 



TABLE 1 

 Physicochemical Characteristics of ICSH from Sheep and Hog 



Pituitary Glands* 



Determinations 



Molecular weight 



Sedimentation content, S X lo'^. 



Isoelectric point, pH 



Tyrosine, per cent 



Tryptophane, per cent 



Mannose, per cent 



Hexosamine, per cent 



Sheep 



40 , 000 



3-6 



4. 60 

 4.50 

 1 .00 



4-45 

 5.86 



Hog 



90 , 000 



5-4 



7 



ca. 3 



2 



45 



80 



* See ref. 2, 10, 11, 12, 14, 15. 



FSH.*'^'^ The latter has been claimed to be "biologically pure,"^ that is, free 

 from all active contaminants, while the best sheep FSH fractions may contain 

 some ICSH, but no other known hormones. 



A considerable amount of work has been done to study the effect of specific 

 reagents on the hormonal activity of the gonadotrophins. Thus, some proteo- 

 lytic enzymes were found to inactivate preferentially either ICSH (LH) or 

 FSH. Crude trypsin was shown to destroy nearly all the ICSH but not the 

 FSH,^'-^ while pepsin leaves intact only the ICSH;^^ on the other hand, ptyalin 

 (saliva) destroys FSH but not ICSH.^ Apparently the high carbohydrate con- 

 tent of the FSH is in some way, possibly only structurally, essential for its 

 activity. Rapid inactivation by treatment with ketene^^ and nitrous acid may 

 be interpreted as evidence for the essentiality of free amino groups for the 

 activity of the gonadotrophins. 



Cysteine also inactivates these hormones, although not as readily as other 

 proteins,^' ^ thus favoring the assumption that the integiity of some disulfide 

 bonds which are not easily reduced is essential for hormonal activity. 



Biological Properties of ICSH 



As the name indicates, this hormone stimulates the interstitial tissue of the 

 gonads of either sex. Its ability to effect repair of this tissue, which atrophies 

 characteristically after hypophysectomy, has been used as a test method in 

 female rats. By this method 5-10 ix%. of the hormone can be detected. Other 



