OXYGEN SUPPLY OF RAT KIDNEY - MEASUREMENTS OF INTRARENAL PO2

Using a newly developed platinum-O2-microeletrode [30] based on the design of Silver [37] the construction and properties of which are described, pO2-measurements in the parenchyma of the blood-perfused and the cell-free perfused rat kidney were carried out. By continuous recording of the pO2 during slow (150 μ×min-1) insertion of the O2-electrode into the respiring tissue two regions of distinctly different mean pO2-values were found. In the outer region which extends from the renal surface to a depth of about 3-4 mm (corresponding anatomically with the renal cortex) large pO2-differences exist close to each other. In the blood-perfused kidney the maximum cortical pO2-values lie in the range of arterial pO2 the lowest values at about 10 Torr. In the cortex of the cell-free perfused kidney the maximum pO2-values lie considerably below the arterial pO2. In both the blood perfused and in the cell-free perfused kidney at centripetal movement of the O2-electrode the cortical region of high and fluctuating pO2 is followed by a narrow zone (≈200 μ radial extension) of a steep decrease of the mean pO2. At further insertion in both preparations the pO2 remains at low pO2-values of ca. 10 Torr. Anatomically, this latter region of low and constant pO2 corresponds to renal medulla and pelvis. By recording the decrease of parenchymal pO2 after sudden stop of the perfusion attempts were made at measuring the critical local O2-supply pressure. In the cortex of the cell-free perfused kidney critical local O2-supply pressures between 6 and 28 Torr with a maximum abundance at 8 Torr were found. The qualitative and quantitative implications of the presented data on the conditions of parenchymal O2-supply are discussed. The results are interpreted as an indication for the arteriovenous shunt (bypass)-diffusion of considerable amounts of oxygen, especially under the conditions of the cell-free perfusion. Furthermore, it follows from the data presented that even at high venous O2-pressures and high mean pO2-values in the parenchyma regions of local anoxia may exist. © 1969 Springer-Verlag.