388 CELLS, TISSUES, AND ORGANISMS 



ably, depending on the time after hypophysectomy, the dose of testo- 

 sterone, the duration of treatment, and the endpoint used ( cf. Simpson 

 et al., 1944; Reiss et al., 1946 ) . Simpson and associates ( 1944 ) found 

 that testosterone, administered in doses of 0.1 or 1.0 mg. per day to rats 

 which had been hypophysectomized for a long period, increased the 

 width of the epiphyseal cartilage. However, when studied under the 

 conditions of the growth-hormone assay, testosterone, in doses of 0.05 

 or 1 mg., failed to produce a detectable change from the control group. 

 Geschwind and Li (1955), using conditions of a growth-hormone 

 assay, reported that 1 mg. of testosterone per day did not alter control 

 cartilage. They noted, however, that a lower dose of testosterone— 0.1 

 mg. per day— produced a small but significant increase in cartilage 

 width. These studies indicate that under certain experimental condi- 

 tions testosterone can increase the width of epiphyseal cartilage. This 

 is particularly true of small doses, for large doses of testosterone may 

 fail to produce a response. 



Testosterone also affects the response to growth hormone in hypo- 

 physectomized rats, the effect produced depending on the dose admin- 

 istered. In the studies of Geschwind and Li (1955) 1.0 mg. of testos- 

 terone per day augmented the growth-hormone response (Table 1). 



TABLE I 



Effect of Testosterone Propionate on Response to 

 Growth Hormone (Geschwind and Li, 1955) 



However, when the dose of growth hormone was sufficient in itself to 

 produce a maximal response, the same dose of testosterone was with- 

 out an augmenting effect ( Simpson et ah, 1944 ) . Conversely, when the 

 dose of growth hormone was low, but still sufficient to produce a sig- 

 nificant response, Geschwind and Li (1955) observed that 0.1 mg. of 

 testosterone markedly enhanced the response. The employment of a 

 high dose of testosterone, namely, 4 mg. per day, was reported by 

 Reiss et al. ( 1946 ) to inhibit the action of growth hormone. 



These data, demonstrating an effect of testosterone in the hypo- 

 physectomized rat, the potentiating effect of testosterone on growth- 

 hormone response, and the ability of large doses of testosterone to 



