Cu(II) complexation potentiates arginine vasopressin action on nonpregnant human myometrium in vitro

Copper may influence in vivo and in vitro uterine activity. Recent evidence has shown that cupric ions can easily form complexes with oligopeptides like arginine vasopressin (AVP). The high complex stability in vitro suggests a possibility of complex formation in vivo, in the uterus of intrauterine device users. In vitro isometric contractions were recorded in uterine tissues from nonpregnant premenopausal women undergoing hysterectomy and the effect of Cu-AVP complex on isolated human nonpregnant myometrium was investigated. The addition of the Cu(II)-AVP complex to the bath medium led to a concentration-dependent increase of the contractile activity. The activity was somewhat lower for the complex (-log EC(50) of 8.5 +/- 0.2, n = 7) than for AVP, but the difference was not statistically significant (p = 0.11). The maximal responses (E(max)) of the myometrium strips treated with AVP and the Cu (II)-AVP complex did not differ significantly. To assess the effect of presence of Cu (II) in the medium on tissue response to AVP, myometrium strips were preincubated for 20 min in the medium containing 10(-6) mol/L Cu(II) prior to the administration of AVP. The chosen Cu (II) concentration was below the threshold of effect on the spontaneous contractile activity in our experiments. The presence of cupric ions in the bath caused a significant leftward shift in the concentration-response curve to AVP.