Abstract
Changes in oxidative capacities and phospholipid remodeling accompany temperature acclimation in ectothermic animals. Both responses may alter redox status and membrane susceptibility to lipid peroxidation (LPO). We tested the hypothesis that phospholipid remodeling is sufficient to offset temperature-driven rates of LPO and, thus, membrane susceptibility to LPO is conserved. We also predicted that the content of LPO products is maintained over a range of physiological temperatures. To assess LPO susceptibility, rates of LPO were quantified with the fluorescent probe C11-BODIPY in mitochondria and sarcoplasmic reticulum from oxidative and glycolytic muscle of striped bass (Morone saxatilis) acclimated to 7°C and 25°C. We also measured phospholipid compositions, contents of LPO products [i.e., individual classes of phospholipid hydroperoxides (PLOOH)], and two membrane antioxidants. Despite phospholipid headgroup and acyl chain remodeling, these alterations do not counter the effect of temperature on LPO rates (i.e., LPO rates are generally not different among acclimation groups when normalized to phospholipid content and compared at a common temperature). Although absolute levels of PLOOH are higher in muscles from cold- than warm-acclimated fish, this difference is lost when PLOOH levels are normalized to total phospholipid. Contents of vitamin E and two homologs of ubiquinone are more than four times higher in mitochondria prepared from oxidative muscle of warm- than cold-acclimated fish. Collectively, our data demonstrate that although phospholipid remodeling does not provide a means for offsetting thermal effects on rates of LPO, differences in phospholipid quantity ensure a constant proportion of LPO products with temperature variation.