The reduction of a nitroxide spin label as a probe of human blood antioxidant properties.
The kinetics of reduction of the radical R*, 5-dimethylaminonaphthalene-1-sulfonyl-4-amino-2,2,6,6-tetramethyl-1-piperidine-oxyl by blood and its components were studied using the EPR technique. The results demonstrate that R* is adsorbed to the outer surface of the membrane and does not penetrate into the erythrocytes. A series of control experiments in PBS demonstrate that ascorbate is the only natural reducing agent that reacts with R*. The observed first order rate of disappearance of the nitroxide radical k, is: k(blood) > k(eryth) > k(plasma) and k(blood) approximately = k(eryth) + k(plasma). The results demonstrate that: a. The erythrocytes catalyze the reduction of R* by ascorbate. b. The rate of reduction of the radical is high though it does not penetrate the cells. c. In human erythrocytes there is an efficient electron transfer route through the cell membrane. d. The study points out that R* is a suitable spin label for measuring the reduction kinetics and antioxidant capacity in blood as expressed by reduction by ascorbate.
Saphier
O
O
Department of Chemistry, Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Silberstein
T
T
Shames
A I
AI
Likhtenshtein
G I
GI
Maimon
E
E
Mankuta
D
D
Mazor
M
M
Katz
M
M
Meyerstein
D
D
Meyerstein
N
N
D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000737:chemistry; D001774:Blood Chemical Analysis; D002462:Cell Membrane / Q000378:metabolism; D003497:Cyclic N-Oxides / Q000737:chemistry; D003619:Dansyl Compounds / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D004912:Erythrocytes / Q000737:chemistry / Q000378:metabolism; D005295:Ferrocyanides / Q000737:chemistry; D006400:Hematocrit; D006801:Humans; D007700:Kinetics; D008280:Magnetics; D009281:Naphthalenes / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D013113:Spin Labels; D013997:Time Factors
C476924:5-dimethylaminonaphthalene-1-sulfonyl-4-amino-2,2,6,6-tetramethyl-1-piperidine-oxyl; D000975:Antioxidants; D003497:Cyclic N-Oxides; D003619:Dansyl Compounds; D005295:Ferrocyanides; D009281:Naphthalenes; D010880:Piperidines; D013113:Spin Labels; C031721:naphthalene; D009569:Nitric Oxide; C020354:hexacyanoferrate II; D001205:Ascorbic Acid; C001803:tempol