Fraenkel-Conrat, Li, and Simpson 187 



effects in the female become evident only in combination with P'SH and will 

 be discussed later. In male rats, stimulation of the interstitial tissue leads to 

 androgen secretion, thus offering a functional test method for this hormone. 

 It has been shown, however, that the ability of all pituitary extracts and frac- 

 tions to stimulate androgen secretion is very poor compared with that of 

 circulating hormones.®'^ Thus, most authors (with the exception of Fevold 

 and co-W'Orkers) find the seminal vesicles of immature normal or hypophy- 

 sectomized rats very insensitive to stimulation by pituitary preparations.* The 

 observation that the ventral prostate of immature hypophysectomized rats 

 (2 days p.o.) was much more sensitive to the secreted androgens than other 

 parts of the accessories has supplied a reliable functional-test method for the 

 interstitial-cell-stimulating hormone."" 



Other effects of this hormone may be less specific. Thus, it increases the 

 testis weight of normal and hypophysectomized rats and, to a greater extent, 

 those of immature pigeons and chicks, an effect which is also produced by 

 FSH. Recently ICSH was also found to favor placentoma formation and pro- 

 long pregnancy in normal rats,^° phenomena which are probably consequent 

 to stimulation of the pituitary by the ICSH. 



Another type of biological activity can be produced with ICSH, that is, that 

 of antagonism. Upon intraperitoneal administration, this hormone will de- 

 crease the activity of other gonadotrophins (such as pregnant-mare serum) 

 simultaneously administered.^^ 



Biological Properties of FSH 



As the name indicates, the primary effect of this hormone in the female is 

 the stimulation of the development of follicles. In hypophysectomized rats, 

 only 2-3 jxg. of the most active preparations from sheep pituitaries are needed 

 for this effect." Pig FSH fractions which have been described as "biologically 

 pure," that is, free from other active principles, are considerably less active.^ 

 The follicular giowth elicited with purified FSH is associated with only lim- 

 ited increases in the weights of the ovaries, which rarely exceed 60 mg. 



Follicles produced with FSH alone seem to secrete less estrogenic substances 

 than those produced by unfractionated extracts, as judged by uterine de- 

 velopment. According to Creep and his associates, "biologically pure" pig 

 FSH was found to result in no uterine stimulation, even at very high dosage.^ 

 Sheep FSH has not been obtained similarly free from estrogenic properties." At 

 sufficiently high levels (ten- to fiftyfold the MED) in hypophysectomized rats 

 it produces estrus, corpora lutea, and repair of the interstitial tissue in female 

 and ventral prostate growth in male rats. From these findings it could be con- 

 cluded that the best sheep FSH fractions still retain 10-20 per cent ICSH. The 

 action of FSH preparations on interstitial tissue was found to differ, however, 



* ICSH maintains the accessories of adult male rats after hypophysectomy but docs not 

 produce, in any type of rat, hypertrophy comparable to that elicited with secreted gonado- 

 trophins. 



