Change of potassium current density in rabbit corneal epithelial cells during maturation and cellular senescence

Background: Voltage-gated potassium (K+) channels may participate in cellular developmental regulation, including cell differentiation, proliferation and apoptosis. This study investigated the change of K+ current densities in corneal epithelial cells during maturation and cellular senescence. Methods: New Zealand white rabbits were divided into three age groups: newborn (<= 7 days old, n = 18); young (8-12 weeks old, n = 59); and adult (20-28 weeks old, n = 16). Rabbit Corneal epithelial cells were subdivided into the following three groups: small cells with capacitance < 6.0 pF; medium cells with capacitance 6.0-10.0 pF; and large cells with capacitance > 10.0 pF. Using a whole-cell clamp technique, K+ current was recorded and current densities were calculated. Differences in K+ current densities among newborn, young and adult rabbits, as well as differences among small, medium and large cells, were analyzed. Results: We delineated two types of cells manifesting different amplitudes of depolarization-activated K+ outward currents. The averaged current density of type 1 response cells was significantly larger than that of type 2 cells in newborn, young, and adult groups. For newborn epithelial cells, the depolarization-gated outward K+ current density decreased from small to medium to large cells (p = 0.049, at a membrane potential of 140 mV). A similar pattern of change in current density was also delineated for these cell sizes in young and adult rabbit corneal cells (p < 0.001 for both young and adult rabbits). An increase in depolarizationgated outward K+ current density was also delineated from newborn to young to adult rabbits (p < 0.00 1, p < 0.001 and p < 0.006 for small, medium and large cells, respectively, at a membrane potential of 140 mV). Conclusions: Corneal epithelial cells expressed K+ channel densities that were distinct from basal to superficial cells and from newborn to adult rabbits.