THE EFFECT OF OUABAIN ON THE HYDRATION AND THE ADENOSINE TRIPHOSPHATASE ACTIVITY OF THE CORNEA

¹ Ophthalmological Research Unit, The W. K. Kellogg Foundation Laboratories, The Wilmer Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland

The adenosine triphosphatase activity of the cornea has been measured and a comparison made of the effect of varied concentrations of ouabain on both the ATPase activity of the tissue and on the hydration of the cornea under in vitro and in vivo conditions. Ouabain had no significant inhibitory effect on the ATPase of homogenates of corneal epithelium at concentrations less than 10^-4 M. An inhibition of approximately 10% in the ATPase activity was found with 10^-3 M ouabain. In the absence of sodium or potassium ions, the ATPase activity decreased by an average of 11% and the addition of ouabain did not significantly increase the inhibition.

Ouabain 10^-6 and 10^-5 M was found without effect on swelling of the cornea of the enucleated eye immersed in an oxygenated Ringer phosphate solution. Ouabain 10^-6 and 10^-5 M was also without effect on the extrusion of water and electrolyte from the cornea after swelling induced by cooling for 18 hours. In comparison, 10^-4 M ouabain caused significant swelling of the cornea in the enucleated eye immersed in Ringer phosphate and completely inhibited the active extrusion of water and electrolytes from the cornea after cold-induced swelling.

In living anesthetized rabbits, bathing the cornea with Ringer phosphate containing 10^-6, 10^-5 or 10^-4 M ouabain for 5 hours failed to cause swelling of the cornea.

The significance of these results to the understanding of the mechanism regulating corneal hydration and the role of the (Na + K) iondependent ATPase is discussed.