Xlvi. the Oxytocic Hormone of the Posterior Lobe of the Pituitary Gland

IN Part V [Gulland and Randall, 1935] it was shown that the molecule of the oxytocic hormone certainly contains one, and may possibly contain two, oxidation-reduction systems, although the existence of the second is not definitely established. The present communication describes the actions on the hormone of some oxidising and reducing agents, which were studied in the hope that they might throw light on the nature of the groups forming the oxidation-reduction system, or systems. EXPERIMENTAL. Sulphur dioxide and sodium sulphite (Fig. 1). Sodium sulphite at PH 8-4 caused irreversible and complete inactivation of the hormone in 5 minutes. Sulphur dioxide at PH 3 5, on the other hand, caused a slower inactivation to about 60 %, which was followed by reactivation and finally by inactivation to 3-6 % after 24 hours.