Physiological microassay of plasma total antioxidant status in a model of endothelial dysfunction in the rat following experimental oxidant stress invivo

We have developed a photometric microassay for the assessment of total anti oxidant status in plasma at physiological pH and temperature and applied it to evaluate experimental oxidant stress in vivo associated with endothelia l dysfunction in vitro. Rat plasma or L-ascorbic acid inhibited the peroxid ase-mediated accumulation after 6 min at pH 7.4 and 37 degrees C of ABTS(+) (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical), measured at 405 nm, in a concentration-dependent manner. Plasma total antioxidant st atus, expressed as the ascorbate equivalent antioxidant concentration, was subsequently found to be significantly reduced in rats treated daily for 7 days in vivo with the oxidant compounds hydroquinone (50 mg/kg i.p.) and tr iethylenetetramine (100 mg/kg i.p.), either alone or in combination with th e glutathione-depleting agent L-buthionine sulfoximine (50 mg/kg i.p). Furt hermore, basal endothelial function in isolated aorta was impaired after hy droquinone or triethylenetetramine in a manner aggravated by L-buthionine s ulfoximine. (C) 1999 Elsevier Science B.V. All rights reserved.