NITROXIDE FREE-RADICAL CLEARANCE IN THE LIVE RAT MONITORED BY RADIOFREQUENCY CW-EPR AND PEDRI

The use of RF (100 to 300 MHz) PEDRI and CW-EPR techniques allows the in vivo study of large animals such as whole rats and rabbits. Recentl y a PEDRI instrument was modified to also allow CW-EPR spectroscopy wi th samples of similar size and under the same experimental conditions. In the present study, this CW-EPR and PEDRI apparatus was used to ass ess the feasibility of the detection of a pyrrolidine nitroxide free r adical ,2,5,5,-tetramethylpyrrolidine-1-oxyl-3-carboxylic acid, PCA) i n the abdomen of rats. In particular, we have shown that after the PCA administration (4 mmol kg(-1) b.w.): (i) the PCA EPR linewidth does n ot show line broadening due to concentration effects; (ii) a similar P CA up-take phase is observed by EPR and PEDRI; and (iii) the PCA half- lives in the whole abdomen of rats measured with the CW-EPR (T-1/2 = 2 6 +/- 4 min, mean +/- sd, n = 10) and PEDRI (T-1/2 = 29 +/- 4 min, mea n +/- sd, n = 4) techniques were not significantly different (p > 0.05 ). These results show, for the first time, that information about PCA pharmacokinetics obtained by CW-EPR is the same as that from PEDRI und er the same experimental conditions.