Epinephrine oxidation to adrenochrome is a sensitive method for detecting superoxide and is applicable to tissues
(Mirsa & Fridovich 1972).
Epidermal strips prepared by homogenizing were incubated in the opening medium containing 10 mM CaCl2 for 2 h in the dark.
The strips were transferred to the control medium [10 mM MES-KOH, pH6.15, 50 mM KCl, 110 mM CaCl2, 100 mM ethylenediaminetetraacetic acid (EDTA), 1 mM epinephrine] or the controlmedium containing 10 mM of ABA.
The superoxidegenerating activity was assayed spectrophotometrically by measuring the oxidation of epinephrine to adrenochrome at 480 nm. Adrenochrome-producing activities were calculated using the molecular absorption coefficient of 4020.