The activation of chloride transport by epinephrine and Db cyclic-AMP in the cornea of the rabbit.

Abstract

The addition of epinephrine to the solution bathing the epithelial side of the isolated rabbit cornea produced a biphasic increase in the short-circuit current with little or no change in the potential difference. Addition of aminophylline or theophylline, produced prolonged stimulation of the current, presumably through inhibition of phosphodiesterase. Db cyclic-AMP produced a rapid and sustained increase of the current as well as a large increase in the net transport of chloride ions from endothelial to epithelial side. This chloride pump, activated by an elevation of cyclic AMP, is located in the epithelium of the rabbit cornea. In Cl-free solutions no activation by these compounds of the remaining sodium current was found. The cyclic-AMP content of corneas incubated in the presence of theophylline and epinephrine was significantly increased. It is concluded that epinephrine influences the function of the rabbit corneal epithelium by increasing the level of cyclic AMP which activates a chloride pump operating toward the tear side. The implications of the presence of this chloride pump are discussed.