pO(2) measurement in murine tumors by Eppendorf 'Histograph'

The purpose of this study was to assess the usefulness of the Eppendorf 'Kistograph' as a device for measuring pO(2) in tumor and normal tissues of the laboratory mouse. To determine the appropriate calibration and electrode condition, nitrogen bubbling time was changed, and the current during calibration was recorded. Reproducibility of pO(2) measurements was tested in the series of human xenografts and murine isoplants at different time points or in the same tumor in successive determinations. pO(2) values obtained with the Eppendorf 'Histograph' were compared to those obtained with a manually controlled needle-type electrode manufactured by the Diamond-General Company. The pO(2) values after 9 min of nitrogen bubbling were closer to the expected values than those after 3 min bubbling. The current during nitrogen bubbling in calibration declined following the pO(2) measurement by an amount corresponding to 0.8 mm Hg. Good reproducibility of pO(2) measurement was shown in i) pO(2) values in the same cell line at different time points and ii) pO(2) values in two or three consecutive measurements in related regions within the same tumor. The Eppendorf 'Histograph' and the Diamond-General device showed no significant differences in pO(2) distribution in either subcutaneous tissue or MCaIV tumors. In conclusion, results of the Eppendorf 'Histograph' were consistent and reproducible and were similar to those obtained by the Diamond-General set-up.