USE OF EPR OXIMETRY WITH INDIA INK TO MEASURE THE PO(2) IN THE LIVER IN-VIVO IN MICE

The partial pressure of oxygen (pO(2)) of the liver in vivo in unanest hetized mice was determined using electron paramagnetic resonance (EPR ) oximetry with India ink, The EPR spectra were obtained using a low-f requency (1.2 GHz) EPR spectrometer with a loop gap cavity resonator, The line width of the India ink used in this experiment was reversibly broadened by oxygen and was particularly sensitive to pO(2) below 30 torr, After the administration of India ink into the tail vein, the In dia ink particles were taken up mainly by Kupffer cells in the liver a nd in part by phagocytes in the spleen, The pO(2) measured in the norm al liver was about 14 torr and was constant for the P-week experimenta l period, The pO(2) decreased when measured at 1, 2, and 6 days after treatment with a hepatotoxin (carbon tetrachloride (CCl4)); within 2 w eeks, it returned almost to the initial level, Measurements by EPR at sacrifice of controls and CCl4-treated mice indicated that more than 9 0% of the India ink went to the liver; the spleen contained 4.7% of to tal amount in control mice and 8.8% in CCl4-treated mice when measured 2 weeks after the treatment. These data indicate the usefulness of In dia ink for measuring the pO(2) of the liver in vivo and that the pO(2 ) in the Kupffer cells is decreased when the liver is damaged by CCl4.