Diffusion of oxygen in slices of rat brain

A new method for the joint determination in tissue slices of the diffusion coefficient of oxygen (D) and the fluorescence-quenching coefficient (K') of pyrenebutyric acid (PBA) is introduced. Values of D and K' in rat brain at temperatures (Tc) from 20 to 40 degrees C were determined and referred to the values in water. D = DH2O (0.72 - 0.0074 Tc) +/- 0.079 X 10(-5) cm2/s for 80-microns slices. D = DH2O (1.01 - 0.0074 Tc) +/- 0.12 X 10(-5) cm2/s for 160-microns slices. K' = K'H2O (0.72 + 0.025 Tc) +/- 0.56 X 10(-4) mmHg-1. The temperature dependence of both these parameters in tissue is different from their temperature dependence, and comparison with parameter values obtained with other methods leads us to conclude that factors affecting the diffusion of oxygen in tissue are heterogenous rather than homogenous. The variation in the different parameters, D and K', probably exceeds a twofold range.