Lipid radical generation in polar (Laternula elliptica) and temperate (Mya arenaria) bivalves

Lipid peroxidation in Laternula elliptica was assessed employing detection of lipid radicals by electronic paramagnetic resonance measurements. The values were compared with the data from the temperate mud clam Mya arenaria. Lipid radical content was higher in the Antarctic bivalve as compared to the temperate mud clam, even within the range of its habitat temperature. The rate of generation of lipid radicals was affected by the iron content in the samples. The iron content in individual samples of digestive glands from Laternula elliptica ranged from 3 to 6 nmol g-1fwt and from Mya arenaria from 0.6 to 2.7 nmol g-1fwt. Arrhenius plots, developed from the rates obtained in the presence of 25 mM iron, showed no significant differences between the activation energy calculated for digestive glands of Laternula elliptica and Mya arenaria. The Fe3+ reduction rate by Laternula elliptica was higher than the rate measured in Mya arenaria (4.7 ± 0.9 and 1.8 ± 0.4 nmol mg-1 protein min-1, respectively). A higher content of both a-tocopherol and b-carotene was measured in Laternula elliptica as compared to Mya arenaria. The reported data suggest that increased lipid radical content in the membranes of cold adapted organisms could be also related to iron content.