Transcorneal Potential in Vivo

Introduction  Of recent interest has been the finding of Donn, Maurice, and Mills¹ of a transcorneal potential difference (p.d.) across the rabbit cornea in vitro. In an additional paper,² these authors measured the Na²⁴ fluxes across the cornea in vitro and reported that there is a net inward flux of sodium from the epithelial side of the cornea into the stroma during short-circuiting of the p.d. across the cornea. Since the net inward flux was almost equivalent to the neutralizing current during short-circuiting of the p.d., the authors concluded that sodium is actively transported across the epithelium into the corneal stroma and that it is this active transport which accounts for the transcorneal potential.The finding of a net inward flux of sodium from the epithelial side of the cornea into the stroma is paradoxical to the extent that movement of sodium ion in this direction would