In vitro Production and Inhibition of Aortic Vasoconstriction by Mercuric,Cadmium,and Other Metal Ions. ∗

Summary

Low concentrations of mercuric ion induced slow steady contractions of spirally-cut strips of thoracic aorta from normal rabbits. The shortening of the strip was 2.5% with 10⁻⁷ molar and 21% with 10⁻⁴ molar mercuric ion. Such a contraction was preceded by a latent period and followed by spontaneous relaxation, after which the strip was refractory to the original stimulus. Cadmium ions did not induce contractions, but did inhibit those induced by lower concentrations of mercuric ions. Both mercuric and cadmium ions inhibited 1-epinephrine; mercuric, but not cadmium, ions inhibited angiotensin II. Zinc ions were inert. Silver cupric, cuprous, barium, mercurous, and vanadyl ions induced contractions but only in concentrations greater than 10⁻⁶ molar, Relatively high concentrations of two sulfhy-dryl-binding agents inhibited contractions induced by the mercuric ion; whereas low concentrations of a chelating agent markedly augmented them.