Adenosine-5 ′-triphosphate-induced Intracellular Calcium Changes through Gap-junctional Communication in the Corneal Epithelium

Abstract

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 μM). [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.