%0 Journal Article %A H. Shida %A M. A. Meyers %A S. B. Barker %T EFFECT OF COPPER IN THYROXINE POTENTIATION OF IN VITRO EPINEPHRINE ACTION ON SMOOTH MUSCLE %D 1963 %J Journal of Pharmacology and Experimental Therapeutics %P 280-284 %V 141 %N 3 %X The helical aortic strip described by Furchgott and Bhadrakom has been used to test enhancement of epinephrine and norepinephrine by in vitro addition of thyroxine. No such action was seen when the copper content of the Krebs-Ringer medium was as low as 1.5 µg/liter, but was clearly evident at copper levels of 3.5 and 6.6 µg/liter. Ethylenediaminetetraacetate had a similar effect and it was concluded that the effects of both substances can best be explained by their chelation of copper as a contamination of ordinary working solutions. It was noted that zinc and iron salts added in higher concentrations (100 µg/liter) also suppressed catecholamine action and were likewise corrected by thyroxine. Manganese at 10 µg/liter was as effective as copper, but was not reversed by thyroxine. %U https://jpet.aspetjournals.org/content/jpet/141/3/280.full.pdf