Reaction kinetics analysis to estimate in vivo decay rate of EPR signals of a nitroxide radical in the brain and the inferior vena cava of rats |
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Authors: | Email author" target="_blank">H?YokoyamaEmail author M?Tada O?Itoh K?Fukui |
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Institution: | 1.Institute for Life Support Technology,Yamagata Public Corporation for Development of Industry,Yamagata,Japan;2.Regional Joint Research Project of Yamagata Prefecture,Japan Science and Technology Corporation,Yamagata,Japan |
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Abstract: | To clarify the degree of the influence of the peripheral organs on the temporal changes in the electron paramagnetic resonance
(EPR) signal intensity of a nitroxide radical permeating the blood-brain barrier, 3-hydroxymethyl-2,2,5,5-tetramethylprrolidine-1-oxyl
(hydroxymethyl-PROXYL), in the brain, temporal changes in the EPR signal in the brain or inferior vena cava of rats were measured
by an in vivo 700 MHz radio-frequency EPR spectrometer equipped with a bridged loop-gap resonator or a surface-coil-type resonator.
In all measurements, good linearity was observed on semilogarithmic plots of the signal intensity against time after the hydroxymethyl-PROXYL
injection. From these plots, the reaction rate and the initial level of hydroxymethyl-PROXYL in the brain and the vena cava
were calculated. A mathematical model expressing the nitroxide radical concentration in the brain, which is connected to other
organs via the circulatory system, was made. With this model and the results of the EPR measurements, the degrees of influence
of the nitroxide reduction in the brain and the other organs were simulated. It was found that the reaction rate (equal to
log2/half-life) of hydroxymethyl-PROXYL observed in the brain reflected the reduction of hydroxymethyl-PROXYL there and was
not influenced by the reduction in other organs. |
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Keywords: | |
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