Adenosine-5'-triphosphate-induced intracellular calcium changes through gap-junctional communication in the corneal epithelium.

PURPOSE To investigate intercellular communication in the corneal epithelium, changes in the concentration of intracellular Ca(2+) ([Ca(2+)](i) ) induced by adenosine-5'-triphosphate (ATP) were analyzed. METHODS Rabbit corneal epithelia were loaded with Ca(2+) indicators and then stimulated by ATP (10 microM). [Ca(2+)](i) changes were monitored by means of conventional fluorescence and real-time confocal microscopy. The localization of connexin 50 (Cx50) was also immunohistochemically examined. RESULTS ATP was found to induce [Ca(2+)](i) increase, which was often synchronized among adjacent cells. When wing cells were topically stimulated by treatment with ATP, the [Ca(2+)](i) increase spread to adjacent wing cells, but significant increase in [Ca(2+)](i) in the superficial and the basal cell layers was not observed. The propagation of the [Ca(2+)](i) change was suppressed in the presence of octanol (1 mM), a gap junction inhibitor. Immunohistochemical staining of Cx50 was strongly detected in the wing and basal cells, but faintly in the superficial cells. CONCLUSIONS There was intercellular communication accompanied by [Ca(2+)](i) changes in wing cell layers, but not in superficial or basal cell layers. The difference in [Ca(2+)](i) changes among the layers of the corneal epithelium suggests that the response of each cell layer plays a distinct role in proliferation and differentiation during recovery of the corneal epithelium.