Measurement of tissue oxygen with a fluorescent probe.

Evidence is presented that pyrenebutyric acid is nontoxic at the concentrations required for the measurement of fluorescence quenching by physiological concentrations of oxygen. It appears that this molecule can be used to measure tissue oxygen since it does not interfere with oxygen consumption. Equally, tissue components do not interfere with the quenching of fluorescence to such an extent as to invalidate the method. The spatial resolution of the technique is limited by some tissue geometrical factors which do not, however, appear to be great enough to prevent its use to measure intercapillary oxygen gradients.