PARS GLANDULARIS AND LACTATION 



hand, lactation may occur in spite of the continued injection 

 of an oestrogen into mammals like the rat and rabbit. 



A distinction should be made between the formation and 

 storage of lactogenic hormone and its release in adequate 

 amounts into the circulating blood. Recent experiments fur- 

 nish us with some information on the effects of oestrogens on 

 the storage of lactogenic hormone. Reece and Turner (1937) 

 reported that the total amount (and often the concentration) 

 of lactogenic hormone in the rat's anterior pituitary is in- 

 creased following the injection of oestrone or oestradiol 

 benzoate. The pituitary of the ovariectomized rat contained 

 less lactogenic hormone in a lower concentration. Margulis 

 (1936) concluded that the injection of "folliculin" into cas- 

 trated rabbits is accompanied by an increase in the content 

 of lactogenic hormone in the pituitary. However, Margulis 

 used only a few animals."" 



The inhibitory effect of oestrogens on lactation has been 

 studied by other authors. Folley and White (1937) injected 

 into male or female pigeons 5 mg. of oestradiol benzoate, fol- 

 lowed a few days later by a dose of lactogenic hormone suffi- 

 cient to cause a marked hypertrophy of the crop-glands. In 

 birds also receiving oestradiol benzoate the hypertrophy of the 

 crop-glands was only about one-half (males) to three-fourths 

 (females) that in control birds. The injection of large doses 

 of oestrogens may inhibit normal lactation in rats, guinea 

 pigs, and rabbits (Folley and Kon, 1938; Mugnai, 1937; 

 Smith and Smith, 1933; Custo, 1937). Folley and Kon ob- 



'•* In Wiegand's experiments (1937) ovarian secretion "as stimulated in rats, 

 initially immature, by the injection of 100 rat-units of prolan daily for 15-20 days. 

 The amount of lactogenic hormone in the pituitary was much greater than in con- 

 trol animals receiving no prolan. If, however, the injections were stopped and the 

 ovaries were removed, lactation appeared after about 36 hours. At that time there 

 had occurred a marked fall in the lactogenic action of the pituitary in agreement 

 with the view that stored hormone had been discharged. Such an effect of gonad- 

 ectomy was not observed in normal rats. 



In other reports (1937) Wiegand attributed the marked increase in the amount of 

 lactogenic hormone in the pituitary immediately following delivery to an increased 

 formation of the hormone caused by the loss of the inhibitory effect of oestrone be- 

 lieved to be present during pregnancy in the rat. 



f 161 1 



