MAMMARY GLAND AND LACTATION 



599 



O2 Uptake 



G\ 



ucose 



uptake 



Lactic acid 

 production. 



s 12 

 ■Hours 



Fig. 10.4. Oxygen uptake, respiratory quotient, glucose uptake, and lactic acid production 

 of mammary gland slices from lactating rats killed at various times after weaning (A — A) 

 and from rats in which svickling was maintained, but in which the galactophores of certain 



glands were ligatured (• •) to prevent the escape of milk, the nonligatured glands 



(O O) acting as controls. (Courtesy of Dr. M. L. McNaught.) 



be that the I'eal basis for the categories is 

 to be found largely in differences in endoge- 

 nous progesterone production by the adrenal 

 cortex. 



The first category comprises those in 

 which estrogens, in what are believed to be 

 physiologic doses, evoke primarily and 

 mainly duct growth; alveoli may appear, 

 but only if high doses are given and the 

 administration is prolonged. Examples of 

 this class are the mouse, rat, rabbit, and cat. 

 Silver (1953a), using the relative-growth 

 technique, has obtained information on the 



levels of estrogen necessary for normal 

 mammary duct growth in the nonpregnant 

 rat. In the young ovariectomized rat, the 

 normal mammary growth rate was best imi- 

 tated by injecting 0.1 ;u,g. estradiol dipro- 

 pionate every second day (from 21 days of 

 age) and increasing the dose step- wise with 

 body weight. In the ovariectomized mouse, 

 Flux (1954a) found it necessary to give 

 0.055 /jLg. estrone daily to attain mammarv 

 duct growth comparable with that obser\-( . i 

 in intact mice. 



In the second category are those s]:»ecies 



