Intercellular spaces in chemically fixed corneal endothelia are related to solute pump activity not to solvent coupling.

1. Stereological analyses of the lateral intercellular spaces in the endothelium of rabbit corneas after chemical fixation were undertaken. 2. Immediately preceding chemical fixation the endothelia were in one of four transport modes: (a) bicarbonate pump activated and no coupled solvent flux, (b) bicarbonate pump activated and, coupled to it, a solvent flux, (c) no fluxes across the endothelia and (d) passive fluid fluxes across the endothelia. 3. In each transport mode, the intercellular spaces were measured after immersion in a series of fixatives in which the concentration of buffer (sodium cacodylate) was increased. 4. Lateral intercellular spaces were a function of buffer concentration in the fixative and activity of the bicarbonate pump. They were not a function of either solvent coupling or passive solvent flow. 5. It is concluded that the characteristic changes of lateral intercellular spaces, when transport is inhibited, do not indicate the site of local osmotic coupling.