The Action of Oestradiol Benzoate on the Activities of Some Polypeptidases in the Hypothalamus of the Pregnant Rabbit After Blastocyst Implantation

Abstract

The administration of oestradiol to pregnant animals can, in certain instances, cause a delay in the onset of parturition (Hain 1935). One of the effects of excess oestradiol may be on the hypothalamus, impeding the release of oxytocin. The purpose of the present study was to note the effect of oestradiol monobenzoate on the activities of certain hypothalamic enzymes which are capable of inactivating oxytocin. In the pregnant animal, oestradiol depressed enzyme activity, and this is interpreted as indicating an inhibitory action of the hormone on the hypothalamus. The inhibitory action is opposite to that produced by the hormone in the non-pregnant animal (Hooper 1968a), and involvement of the corpus luteum or placenta seems probable.