Diffusion of oxygen through the mouse ear

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Abstract
O2 tension differences across the mouse ear were measured polarographically under conditions of no blood flow. For some experiments the ear was split into 2 by cleavage along the central cartilage plate, and the diffusion of O2 measured in both directions across these asymmetrical preparations. Measurements were also made on ears from which the stratum corneum had been removed by stripping with Sellotape. It was possible to relate these results to a simple multi-layer diffusion model. The main barrier to diffusion of O2 resides in the stratum corneum, whose permeability is estimated to be 1.2 .times. 10-8 ml O2 atm-1 cm-1 s-1. The permeability of the rest of the ear is 4.7 .times. 10-7 ml O2 atm-1 cm-1 s-1. The inhibition of tissue respiration by the local injection of solutions of sodium amytal, potassium cyanide and other substances [deoxyglucose, sodium malonate, sodium azide, sodium fluoride and sodium fluoroacetate] reduced the O2 gradients by factors of between 3 and 7. Cooling the ear from room temperature to 0.degree. C reduced the gradients by a factor of about 4.