THE PITUITARY BODY 



Sealock and Du Vigneaud (1935) assayed the oxytocic prin- 

 ciple by means of its depressor action on the blood pressure of 

 fowls. As the authors point out, troublesome difficulties due 

 to the action of foreign substances (such as those used for 

 chemical manipulation of the hormone) may appear if the 

 isolated guinea pig uterus be employed, whereas these sub- 

 stances may be without effect on the fowl's blood pressure. 

 In addition, several authors have introduced refined methods 

 of determining oxytocic effects both in vitro and in vivo. 



For the assay of the vasopressor principle, Simon (1937) 

 recommends that the effect on the blood pressure of the de- 

 capitated rat be determined. By this method as little as 

 0.0025-0.005 unit (0.00125-0.0025 mg. equivalent of Inter- 

 national Standard Powder) can be detected. Small doses of 

 histamine were found to be without action. The most sensi- 

 tive test for vasopressor (diuresis-inhibiting) hormone is 

 based upon the inhibition of water diuresis in the non- 

 anesthetized dog. If the extract be given intravenously, as 

 little as 0.0001-0.0003 unit may cause a recognizable effect. 



The pharmacology of the oxytocic principle.^ — Newton 

 (1934, 1937) found that the cervix of the uterus of the preg- 

 nant goat or of the rat and guinea pig in pregnancy or in 

 other stages of sexual activity is very insensitive toward the 

 oxytocic principle in comparison with the uterine cornua. 

 According to the findings of Li (1935), the isolated fallopian 

 tube of the monkey is much more sensitive toward posterior- 

 lobe extract during the secretory (corpus luteum) or men- 

 strual phases of the uterus than during the proliferative (fol- 

 licular) phase. Also, spontaneous activity of the fallopian 

 tube tended to be lower during the growth of the ovarian 

 follicle. 



^ The intact, but not the isolated, uterus of the cat, dog, or rabbit relaxes and 

 becomes quiescent in response to the administration of vasopressor hormone. This 

 effect is most readily observed in animals which have received oestrogen previously 

 and is said not to appear if the uterus is pregnant (cat and dog). Robson and 

 Schild (1937) believed that the effect should not be attributed to the vascular action 

 of the hormone (see also Azuma and Kumagai, 1935; Robson, 1936; and Morgan, 

 1937, as well as earlier reports previously reviewed.) 



f 260I 



