Electrical Fields in the Vicinity of Small Wounds in Notophthalmus viridescens Skin

The transepithelial potential (TEP) across the skin of Notophthalmus viridescens hindlimb digits was measured in animals immersed in artificial pond water (APW) that was 1.5 mM in NaCl, 0.06 mM in KCl, and 0.1 mM in CaCl₂, before and after making a wound in the digit tip. Before wounding, the TEP of the digit skin averaged 35.3 mV ± 5.5 mV (S.E.M.), inside positive. After wounding, the TEP at locations distant from the wound approximated the TEP before wounding, but, at points progressively closer to the wound surface, the measured TEP was progressively less. The slope of this change in TEP, the lateral wound potential, averaged 41.7 mV/mm ± 9.5 mV/mm, with the regions closer to the wound being more negative than those away from the wound. When the Na⁺ channels of the outer surface of the external epidermal cells were blocked with benzamil (30 µM in APW), the TEP of the unwounded skin was reversed, to an average of - 14.1 mV ± 3.7 mV (inside negative). After benzamil-blocked digits were wounded, the lateral wound potentials averaged -21.5 mV/mm ± 4.0 mV/mm, with the polarity reversed: regions close to the wound were more positive than those away from the wound. The magnitudes of both the normal and the reversed wound fields are greater than those known to promote the migration of cells in vitro. What remains to be determined is how Notophthalmus viridescens epidermal cells and fibroblasts behave in such fields, and how this behavior relates to the process of wound healing under normal and modulated wound field conditions.