PT  - JOURNAL ARTICLE
AU  - Abele, D.
AU  - Heise, K.
AU  - Pörtner, H. O.
AU  - Puntarulo, S.
TI  - Temperature-dependence of mitochondrial function and production of
reactive oxygen species in the intertidal mud clam <em>Mya arenaria</em>
DP  - 2002 Jul 01
TA  - Journal of Experimental Biology
PG  - 1831--1841
VI  - 205
IP  - 13
4099  - http://jeb.biologists.org/content/205/13/1831.short
4100  - http://jeb.biologists.org/content/205/13/1831.full
SO  - J. Exp. Biol.2002 Jul 01; 205
AB  - Mitochondrial respiration, energetic coupling to phosphorylation and the production of reactive oxygen species (ROS) were studied in mitochondria isolated from the eurythermal bivalve Mya arenaria (Myoidea) from a low-shore intertidal population of the German Wadden Sea. Measurements were conducted both within the range of the habitat temperatures (5-15 °C) and when subjected to heat exposure at 20 °C and 25 °C. Experimental warming resulted in an increase in the rate of state 3 and state 4 respiration in isolated mitochondria. The highest respiratory coupling ratios (RCR) were found at 15 °C; at higher temperatures mitochondrial coupling decreased, and release of ROS doubled between 15 and 25 °C. ROS production was 2-3% of total oxygen consumption in state 3 (0.3-0.5 nmol ROS mg-1 protein min-1) at the habitat temperature, reaching a maximum of 4.3 % of state 3 respiration and 7 % of oligomycin-induced state 4+ respiration under heat stress. Thus, state 4 respiration, previously interpreted exclusively as a measure of proton leakage, included a significant contribution from ROS formation in this animal, especially under conditions of heat stress. Oxygen radical formation was directly dependent on temperature-controlled respiration rates in states 3 and 4 and inversely related to mitochondrial coupling (RCR+) in state 4. Mitochondrial ROS formation is therefore involved in cellular heat stress in this eurythermal marine ectotherm.