Na+ transport across the rabbit corneal endothelium.

It has been reported so far that the Na+ transport across the corneal endothelium is symmetrical and therefore, that there is no net transport. We now report that there is a net Na+ transport across the rabbit corneal endothelium. Instead of measuring the conventional steady-state fluxes, pre-steady state fluxes were measured as a function of time (readings were taken at two minute intervals). This technique is based on a theory, proposed very recently, that the flux ratio (efflux/influx) is independent of time. Both the efflux and influx reached their steady state values about fifteen minutes after the addition of the isotope to one side of the chamber. The net sodium flux was obtained from the difference between the steady state efflux and influx values. The direction of the net Na+ flux was from the stromal to the aqueous side, with a magnitude of 2.3 +/- 0.4 microEq/h.cm2 (n = 11, S.E.M.). The net Na+ transport was inhibited by the presence of ouabain (10(-4)M).