320 Mammary Growth After Hypophysectomy 



of Drs. H. M. Evans and M. E. Simpson and the cooperation of the members 

 of the Institute of Experimental Biology that investigation has been begun 

 and forms the subject of this paper.* 



Procedure 



In all of the experiments reported here, female rats of the Long-Evans strain, 

 60-70 days of age, were used. Hypophysectomy was done by the parapha- 

 ryngeal approach on the day following vaginal cornification, and oophorec- 

 tomy when performed was carried out immediately after hypophysectomy. 

 At necropsy the completeness of pituitary removal was determined. Injec- 

 tion of the various hormonal combinations was begun immediately after 

 operation. The operated rats received thyroxin subcutaneously, usually in a 

 dose calculated to bring the animals' oxygen consumption back to normal 

 (10 /xg. daily) and glucose in doses of 200 mg. given intraperitoneally four 

 times weekly. All other hormones were administered subcutaneously, the sex 

 hormones in 0.1 cc. of sesame oil and the pituitary fractions in 0.5 cc. of 2 per 

 cent butanol in water. Injections were made daily for ten days with necropsy 

 twenty-four hours after the last injection. The first inguinal mammary gland 

 was taken from each rat, spread on filter paper, fixed in 10 per cent formol, 

 stained with alum-carmine and cleared in methyl-salicylate. 



The mammary glands were judged with the aid of a binocular dissecting 

 microscope and placed in one of six different classes depending upon the type 

 and degree of development shown. D refers to glands showing a duct system 

 either completely devoid of alveoli or alveolar buds, or else having only a 

 negligible number of these (pi. 1, fig. 1). Such a gland in 60-70-day-old rats 

 is indicative of regression since rats of this age normally show sparsely distrib- 

 uted alveoli or alveolar buds on a well-developed duct system, for which the 

 designation DAB is used. The gland shown in plate 1 , figme 2 may be consid- 

 ered representative of the upper limits of DAB development and when com- 

 pared with plate 1, figure 1, gives one some idea of the rate at which regression 

 occurs in the ten days following hypophysectomy. Since most of the normal 

 rats showed duct and alveolar mammary development equal to or only slightly 

 less than is shown in plate 1, figure 2, the hormonal combinations used have 

 been judged active on the basis of whether they were able in the first place to 

 maintain this amount of development, and in the second place to cause pro- 

 lactational or lobular growth. Plate 1, figures 3-6, represent a purely arbitrary 

 scale ranging from 1 to 4 +, depending upon the degree of lobulo-alveolar 

 growth (LA) obtained, and may be used in judging the efficacy of the various 

 forms of treatment. Since it is probable that lobulo-alveolar mammary 

 growth may be due to more than one hormone, it has been deemed unnecessary 

 at this time to attempt any estimates of unitage of a lobulo-alveolar growth- 



* My sincere thanks go to Miss F. Carter and Mrs. A. McKnight for hypophysectomizing 

 all of the rats, to Dr. M. E. Simpson for the FSH, to Dr. Oliver Kamm of Parke, Davis and 

 Company, for the estrone and progesterone used in this experiment, and to Dr. H. M. E\ans 

 for the use of all of the facilities of his Institute. 



