OXYTOCIN IN LACTATING AND NONLACTATING WOMEN

Abstract

Blood was collected from lactating and nonlactating women with babies 3-7 months old and tested for oxytocin. A modification of the extraction method of Bisset and Walker (1954) was used. As K+ or HT (5-hydroxytryptamine) in the extracts might be interfering substances, they were removed by dialysis or by adding Dibenamine hydrochloride to the organ bath. The extracts were assayed on the isolated sensitized rat uterus, and oxytocin and another oxytocic substance (O.S.) were differentiated by treatment of the extracts with sodium thioglycollate. The oxytocic activity of the mother''s blood collected immediately prior to breast-feeding the infant did not differ significantly from that during suckling or midway between 4-hourly feedings: moreover, it did not differ significantly from that in the blood of nonlactating mothers. The conclusion is drawn that, in these studies on human subjects, neither oxytocin nor O.S. induces the ejection of milk.