Referenced in: none

Automatically associated channels: Kir2.3

Title: Effects of oxidants on lens transport.

Authors: S Walsh, J W Patterson

Journal, date & volume: Invest. Ophthalmol. Vis. Sci., 1991 Apr , 32, 1648-58

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/1707864

Abstract
Hydrogen peroxide is associated with the development of cataracts. As an oxidant, it can act on the sulfhydryl groups of proteins and alter the transport properties of membranes. A nearly impermeant sulfhydryl binding agent is p-chloromercuriphenylsulfonate (p-CMPS). The changes in the current-voltage relationship of the equatorial potassium current produced by hydrogen peroxide and p-CMPS are similar. The authors studied the effects of p-CMPS to determine the possible effects of binding extracellular sulfhydryl groups. With a vibrating probe and microelectrodes, the authors saw three sequential effects of 0.5-5.0 microM p-CMPS. The first phase was a shift of the reversal potential, which is equivalent to the potassium equilibrium potential, to more negative values. The current-voltage relationship (J vs PD) shifted in a manner opposite to that produced by ouabain. The 86Rb uptake was stimulated. Ouabain blocked this initial phase. The second phase was a decrease in the resistance. The effects seen were similar to those described in other tissues after the intracellular injection of small amounts of Ca++. This second phase was inhibited by the removal of Ca++ from the medium and also by the addition of quinine to the medium. The third phase consisted of a depolarization of the lens. This effect has been described by others with larger concentrations of p-CMPS and is accompanied by an influx of Na+ and Ca++. The results suggested that micromolar quantities of extracellular p-CMPS sequentially stimulate the Na, K-pump; activate Ca(++)-dependent K+ channels; and open nonspecific channels. It is suggested that the second phase may play a role in cateractogenesis.