Mass transfer, storage, and utilization of O2 in cat cerebral cortex.

of 02 in cat cerebral cortex. Am. communication describes a study of in vitro cat cerebral cortex with a micro polarographic oxygen electrode. Profiles of Poe versus depth into the tissue were measured while oxygenated saline at 37 C was flowing over the tissue. The measurements were made in the uncut side of a tissue slice within 5 min after excising the tissue from the animal. From the critical thickness for 02 and the measured oxygen gradients in the perfus-ing solution and in the tissue, the diffusion coefficient for oxygen and the Voq were calculated; and the solubility coefficient was estimated. The experimental findings are consistent with & at about 2 mm Hg, but do not indicate a transport mechanism for 02 in cortical tissue. The diffusion coefficient for cat cerebral cortex was similar to values reported by Krogh for other tissue. The experimental method also provides a direct means of measuring Voz and Do2 in other soft labile tissues not readily amenable to the methods of Warburg and Krogh. A TRANSPORT MECHANISM (facilitated diffusion) for O2 in some tissues has been postulated by Wyman (19), and Longmuir (11, 12) suggests an oxygen carrier in some tissues. In addition, Longmuir (9) describes a dependence of-iro2 on POT in rat liver, whereas Gore (5) describes a similar relationship in frog sartorius muscle; and the studies of Chance (2) on mitochondrial respiration indicate a probable K, (K, being the Paz at which metabolism is reduced to one-half the maximum rate) in all tissues. The availability of a micro oxygen electrode (17) offered a unique approach to these problems. In order to determine what kind of transport mechanism exists in cat cerebral cortex, Po2 profiles were measured in freshly excised tissue. The data were found to be consistent with the classical diffusion equation at Pea values in the range of 25 mm Hg and above. Since the data are consistent with the classical diffusion equation they provide the information necessary for calculation of the rate of consumption and diffusion for 02 in the tissue. The solubility coefficient for oxygen cannot be readily measured by ordinary means in a metabolizing tissue and thus, the Krogh diffusion coefficient (diffusion coefficient multiplied by solubility coefficient) is ordinarily reported. To our knowledge, the method to be described here is the only technique for estimating the solubility coefficient as well as determining the rate of 02 consumption and …