Oxygen diffusion in the trout retina

Oxygen tensions were measured in vivo within the different layers of the rainbow trout retina. Oxygen microelectrodes were advanced in 10 micron increments through the retinas and the PO2 measured at each location. Mean retinal PO2 ranged from 124 mmHg at the retinal-vitreal interface to 381 mmHg at the choriocapillaris. These data reaffirm that the cellular layers of the normal trout retina are continually exposed to supra-arterial oxygen tensions that are known to cause toxicity in other species. The intraretinal PO2 gradient was mathematically characterized and results indicate that the in vivo oxygen profile can be described by a two-component exponential function. In order to gain a better understanding of oxygen delivery to the retina, the data were also subjected to an analysis based upon the classical equation for planar diffusion. The trout retina is an excellent model for studying oxygen diffusion in vivo since this tissue is supplied with oxygen from a single source, thereby simplifying the mathematical analysis. Calculations yielded values of 1.86 X 10(-5) and 0.58 X 10(-5) ml O2 min-1 cm-1 atm-1 (at 9 degrees C) for the Krogh permeation coefficient (DS) for the photoreceptor region and the remaining neural retina, respectively.