Wm. R. Lyons 023 



those of Experiment 8, two of three rats showing maminary growth rated as LA— r-r and one 

 showing LA++ growth. 



Experiment lo. — Three hypophysectoniized-oophorectomized rats Avere injected daily for 

 lo days with lo I.U. of estrone plus 5 mg. of the crude lactogenic extract. No growth was in- 

 duced in the mammary glands, but regression was prevented. The rals gained about 1 o-m. 

 per day in weight. 



Experiment 11. — Three hypophysectomized-oophorectomized rats were injected daily for 

 10 days with 5 R.U. of FSH plus 5 mg. of crude lactogenic extract. The results were similar to 

 those of Experiment 10. 



Experiment 12. — Three hypophysectomized-oophorectomized rats were injected daily for 

 10 days with 10 I.U. of estrone, 2 I.U. of progesterone, and 5 mg. of crude lactogenic hormone. 

 The mammary grow th induced Avas rated as LA^^- in one animal (pi. 1, fig. 4) and LA+ in two. 

 In another experiment in which 1 instead of 2 I.U. of progesterone was used, all three rats 

 showed LA+ growth. The rats gained 1-2 gm. per day in body weight. 



Experiment 75. — Three hypophysectomized-oophorectomized rats Avere injected daily for 

 10 days with 10 I.U. of estrone, 1 I.U. of progesterone, and 60 I.U. of pure lactogenic hormone. 

 The mammary growth induced was rated as barely positive lobulo-alveolar growth in two, 

 while in the third rat, the gland was merely maintained. These rats lost 1-5 gm. in body 

 weight. 



Discussion 



The doses of estrone and progesterone (alone or in combination) used in these 

 experiments failed to stimulate any further growth of the hypophysectomized 

 rats' mammary glands; and they were ineffective in even maintaining the slight 

 alveolar development always present in these rats before hypophysectomy. 

 This was also found to be true in similar animals treated with a pituitary FSH 

 capable of stimtilating the secretion of estrin by the ovary. These findings are 

 in accord with the results obtained by the majority of workers who have at- 

 tempted to stimulate hypophysectomized rats' mammary glands \k\x1\ the sex 

 steroids. Higher doses of the sex hormones in different ratios should be tried 

 before concluding that they are completely ineffective in stimulating mam- 

 mary growth in the hypophysectomized rat. It has been reported that these 

 hormones do stimulate lobulo-alveolar mammary growth in the hypophysec- 

 tomized rabbit.'" 



Purified lactogenic hormone injected into normal rats (2 mg. or 60 I.U. 

 daily) caused excellent lobulo-alveolar mammary growth, but doses of 60-120 

 I.U. daily given to hypophysectomized rats were only capable of preventing 

 or delaying postoperative mammary regression. It is known that lactogenic 

 hormone stimulates the luteal cells to secrete progestin even in the hy- 

 pophysectomized rat, but apparently in these animals the amount of estrin 

 secreted is negligible or insufficient to act ^vith the progestin to cause mam- 

 mary growth. This deduction is made from the fact that when 15-60 I.U of 

 purified lactogenic hormone were given daily to hypophysectomized rats along 

 with either 10 I.U. of estrone, or a pituitary FSH which caused estrin secre- 

 tion, slight lobulo-alveolar growth was induced. The success of this type of 

 treatment was undoubtedly partly due to the secretion of progestin by the 

 activated corpora lutea, but it is also necessary to point out that hypophy- 

 sectomized rats injected with lactogenic hormone consume more food than 



