Possible roles of ENaC and Cl(-) channel in wound closure in Xenopus laevis embryos.

Our previous report showed that rapid wound closure in Xenopus laevis embryos was associated with a decrease in the extracellular concentration of either Na(+) or Cl(-) ions. In this study, we examined the wound closure in Xenopus embryos when epithelial Na(+) channel (ENaC), Na(+)/K(+) ATPase (Na(+) pump) or CICs (members of Cl(-) channel) were blocked by each specific inhibitor. Blockage of ENaC and CIC restricted the rate of wound closure during the first 30 min PW and during the subsequent period, respectively. In contrast, inhibition of Na(+) pump had no effect on the rate of wound closure. Furthermore, simultaneous administration of both ENaC and CIC inhibitors resulted in the cumulative reduction of wound closure. Thus, it is plausible that these ion channels play active roles in wound closure in Xenopus embryos. NPPB is known to inhibit both CIC-2 and CIC-3. Immunohistochemical experiments showed that CIC-3, but not CIC-2, was expressed in Xenopus embryos, suggesting that the reduced wound closure by NPPB was due to blockage of CIC-3. A local enhancement of CIC-3 expression at the leading edge of the wounded epidermis was found to be specific to closing wounds that were kept in 10% NAM. An in vitro wounding assay also showed a pattern of CIC-3 expression at the margin of the scratch wound comparable to the results in vivo. These findings suggest that intracellular translocation of CIC-3 is involved in wound closure. We propose that the ion channels, including CIC-3, play a crucial role in wound closure in Xenopus embryos.