Ionic components of wound currents and the self-referencing ion-selective electrode

O'Hara-Wright and colleagues (2022) describe the injury potential, also called the demarcation current, as a difference in electrical potential between intact epithelium and the site of a wound⁶. In their account the potential at the injury falls and current leaks out from the wound edge, which is the pathway of least resistance, creating an electrical field⁶. They report that similar, steady endogenous fields were identified in the blastema of the amputated digit of human children, as in the amphibian blastema⁶. This describes the current as a whole. It does not say which ions carry it.

Vieira and colleagues (2011) examined the ionic components of current at rat corneal wounds. Aminophylline significantly enhanced chloride influx and stimulated a sodium efflux¹. The authors describe it as a nonspecific phosphodiesterase inhibitor that raises cAMP and so increases chloride transport¹. They say these effects match their earlier observations of larger wound currents and faster healing¹. Ascorbic acid inhibited chloride influx but caused a large sodium efflux². They suggest the sodium efflux may compensate for the lower chloride influx so that the transcorneal potential is maintained².

Baluška and Mancuso (2013) discuss currents measured with vibrating probes at the root apex. They argue that the probes detect prominent currents only because the activity of transition zone cells is highly synchronous⁴. The pattern is a smaller outward peak at the meristematic zone and a prominent inward peak at the transition zone⁴. The authors call the sudden switch from outward to inward at the meristem and transition zone border a mystery⁵. They also note that the current switches back to outward at the next border, with the elongation region⁵.

Chifflet and Hernández (2012) ask how plasma membrane potential could act on the actin cytoskeleton through ion transport systems. They name two main routes. One is that the potential modifies ionic currents and so changes the ionic environment near cytoskeletal binding regions³. The other is that it causes electroconformational changes in transport proteins that propagate to cytoskeletal components³. For the second route they cite the proposal that some ion channels signal through conformational coupling with integrins, irrespective of ionic flux changes³. In the first route, altered ionic currents change the ionic environment near cytoskeletal binding regions.