Effect of oxygen and the lipid spin label TEMPO-laurate on fluorine-19 and proton relaxation rates of the perlluoroehemical blood substitute, FC-43 emulsion

Abstract

The 19F and 1H spin-lattice relaxation ( T 1 −1) rates of a liquid perfluorochemical, perfluorotributylamine, and its emulsified form, FC-43 emulsion, were studied using the inversion-recovery method. Both 19F and 1H relaxation rates were found to be linearly proportional to the partial pressure of oxygen, indicating that oxygen solubility in FC-43 emulsion follows Henry's law and that no specific binding between molecular oxygen and perfluorochemicals occurs. TEMPO-laurate, a water-insoluble lipid spin probe, was found to partition preferentially into perfluorotributylamine. At a concentration of 4.5 × 10 −4 M, it enhanced the relaxation rate of 19F nuclei in FC-43 emulsion by 50% (in the absence of oxygen) and by 32% (in the presence of t atm oxygen) at 37°C. TEMPO-laurate also enhanced the proton relaxation rate in FC-43 emulsion by 18% (in the absence of oxygen) and by 10% (in the presence of 1 atm oxygen) at 37°C. The sensitive response of the 19F spin-lattice relaxation rate to oxygen leads to the hypothesis that this rate may be a sensitive parameter for in situ determinations of oxygen tension in blood vessels perfused with perfluorochemical blood substitutes.