The effect of hydrogen peroxide on isolated body wall of the lugworm Arenicola marina (L.) at different extracellular pH levels

The effect of hydrogen peroxide on the rate of tissue oxygen consumption, o n intracellular pH (pH,) and on malondialdehyde (MDA) accumulation was stud ied in isolated body wall tissue of the lugworm Arenicola marina (L.). H2O2 effects were investigated at various levels of pH(i) by changing medium pH (pH(e)). The largest decrease of tissue oxygen consumption (by 17% below c ontrols), as well as the highest degree of MDA accumulation (four-fold comp ared to control values) after H2O2 exposure were found at acidic pH(e) of 6 .4. This was attributed to the higher redox potential of H2O2 in acidic sol utions. Oxygen consumption at alkaline pH(e) (8.5) was not affected by H2O2 . MDA accumulation in the tissue was considerably lower than at pH(e), 7.4 or 6.4. Despite pH dependent alterations of H2O2 redox potential, we observ ed more or less constant pH, independent acidification of the tissue upon e xposure to H2O2. We attributed the acidification to an inhibition of ATP co nsuming proton equivalent ion transport across the cellular membrane. Inact ivation of carrier proteins is discussed to be responsible for the decrease in tissue oxygen consumption. However, with a larger effect on oxygen cons umption at acidic pH, values, the latter may not be the only explanation, b ut additional impairment of other energy demanding processes may be involve d. (C) 2001 Elsevier Science Inc. All rights reserved.