Influence of cadmium ions on the reactivity of isolated human uterine arteries.

The isometric contractions were recorded for pieces of uterine arteries as well as ascending branches of uterine artery (1-2 mm diameter) obtained from 36 nonpregnant, premenopausal women undergoing hysterectomy. Contractile responses to K(+)-depolarization, noradrenaline, and Ca+2 ions were studied. Cadmium at concentrations 10(-9)-10(-3) M produced no changes of tension in the investigated arteries. Incubation (15 min) with low concentration of cadmium (10(-9)-10(-7) M) evoked an increase of amplitude of K(+)-induced contractions in 50% of investigated vessels. Cadmium at concentrations of 10(-6)-10(-3) M gradually inhibited contractions. The influence of cadmium on contractions evoked by noradrenaline was similar to those on K(+)-induced contractions. In a Ca(2+)-free medium, 10(-5) M cadmium induced tonic contractions and pretreatment with 10(-7) and 10(-5) M cadmium slightly enhanced Ca(2+)-induced contractions. Cadmium concentration of 10(-4) M caused substantial inhibition of Ca(2+)-induced contractions. The results suggest that in the human uterine vessels cadmium is not only a Ca(2+)-channels blocker but also interferes with intracellular mechanisms involved in excitation-contraction coupling.