Abstract
In a planned series of studies of the ways in which human myometrial preparations inactivate oxytocin a pilot study was made with the three synthetic model substrates L-Cystyl-di-β-Naphthylamide, S-Benzyl-L-Cy-steinyl-β-Naphthylamide, S-Benzyl-β-Mercaptopropionyl-β-Naphthylamide and with Oxytocin and Deamino-oxytocin. The syntheses of S-benzyl-β-cysteinyl-β-naphthyl-amide and S-benzyl-β-mercaptopropionyl-β-naphthylamide are described. Incubations with crude extracts from myometria of non-pregnant women and pregnant women in the three trimesters liberated β-naphthylamine from L-cystyl-di-β-naphthylamide and S-benzyl-L-cysteinyl-β-naphthylamide but not from S-benzyl-β-mercaptopropio-nyl-β-naphthylamide. The liberation of β-naphthylamine from L-cystyl-di-β-naphthylamide was competitively inhibited by oxytocin and non-competitively inhibited by deamino-oxytocin. The results are interpreted as giving preliminary evidence for the presence of a thiol-oxido-reductase activity and an amino-peptidase activity in the extracts.