614 



PHYSIOLOGY OF GONADS 



periments on laboratory animals the ap- 

 parent failure in milk secretion could be a 

 secondary effect due to either a toxic action 

 of the estrogen causing an anorexia in the 

 mother, interference with milk ejection, or 

 disturbance of maternal behavior or to toxic 

 effects on the young, whose growth rate 

 serves as a measure of lactational perform- 

 ance, through estrogens being excreted in 

 milk. The evidence to date shows that in 



the intact rat estrogens even in very low 

 doses inhibit milk secretion, their action 

 depending on the presence of the ovary ; the 

 ovarian factor concerned appears to be pro- 

 gesterone, estrogen and progesterone acting 

 locally on the mammary gland and render- 

 ing it refractory to the lactogenic com- 

 plex. In the ovariectomized rat much larger 

 doses of estrogen are necessary to inhibit 

 lactation, and the evidence is not entirely 



Body 



Goat 478 



weight ^^L 

 :.) 45 L 



Plasma Na 

 (m-equiv./l.) ^^^^ 



Plasma K 

 (m-equiv./l 



Milk K 40 - 

 (m-equiv./l.) 30 



Milk Na , 



(m-equiv./l.) - 



Solids-not- 

 fat (%) 



Yield of 

 solids-not- 

 fat (g) 

 Fat (%) 



Milk yield 

 (kg) 



Goat died-* 



5 15 25 4 14 24 

 Mgr. Apr. 



Fig. 10.12i4. Effect of replaconi(>nt tlierapy with (losoxycoiticostcM-oiu 

 c-ortisone aoetate (CA) on milk yield, milk composition, and concent 



(DCA) and 

 tion of Na and K 

 in milk and blood plasma of the goat after adrenalectomy. Duration of replacement therapy 

 (pellet implantation) indicated by horizontal lines; the names of steroids and their mean 

 daily absorption rates are given adjacent to the lines. Note in Figure 12.4 the considerable 

 maintenance of milk vield with DCA alone. See also Figure 12/?. (From A. T. Cowic and 

 J. S. Tindal. J. Endocrinol., 16, 403-414, 1958.) 



