['Copper may influence the in vivo and in vitro uterine activity. Recent evidence shows that cupric ions can easily form complexes with oligopeptides like oxytocin (OXT). The high complex stability in vitro suggests a possibility of complex formation in vivo.', 'In vitro isometric contractions were recorded in uterine tissues from pregnant women undergoing caesarean sections and the effect of OXT and the Cu-OXT complex on isolated human pregnant myometrium was investigated.', 'In the concentration range from 10(-14) to 10(-6)M of OXT alone, pre-formed Cu-OXT complex, and OXT following sample preincubation with Cu(II) salt, nosignificant differences were observed for the following parameters of pregnant uterine smooth muscle contraction: the area under the curve, frequency and amplitude of contraction.'] Does cu ( II ) complexation affect oxytocin action on pregnant human myometrium in vitro?