Meeting Abstract
71.4 Thursday, Jan. 6 Effect of diet on membrane composition and CCO activity in the Eastern red spotted newt (Notophthalmus viridescens viridescens) BERNER, N.J.; Sewanee: The University of the South nberner@sewanee.edu
Eastern red spotted newts are active in the winter. Our previous work shows that they acclimate enzyme activity, metabolic rate, and membrane phospholipid fatty acid (FA) composition in skeletal muscle seasonally, in the laboratory and in the field. Cold-acclimated (8°C) newts have higher skeletal muscle cytochrome c oxidase (CCO) and citrate synthase (CS) activity and higher standard metabolic rates than warm-acclimated (26°C) newts. In addition, in the laboratory, modifications occur in three major polyunsaturated FAs (PUFAs) in skeletal muscle membranes. Cold-acclimated newts have roughly half the mol% of 18:2 n-6 (linoleic) and twice the mol% of 20:4 n-6 (arachidonic acid) and 22:6 n-3 (docosahexaenoic acid) of warm-acclimated newts. Membrane FA composition can affect membrane-bound proteins such as CCO, and metabolic rate. This experiment was performed to test the hypothesis that the change in membrane FA composition that takes place during acclimation is at least partially responsible for the change in CCO activity that occurs concomitantly. This hypothesis was tested by producing artificial changes in membrane FAs driven by diet, and subsequently assessing CCO and CS activity at the whole tissue level. All newts were maintained at 20°C, 12:12 L:D for 6 – 8 weeks in the laboratory. Groups of newts were fed diets featuring four different types of lipids: saturated FAs; monounsaturated FAs; omega-3 PUFAs; or omega-6 (n6) PUFAs. Newts that were fed crickets (high n6-PUFA diet) had significantly higher CCO activity than newts fed other diets at all assay temperatures, whereas their CS activity was not significantly elevated. The CCO/CS ratio was highest in newts fed crickets, reflecting these differences, indicating that the change in CCO activity could be due to membrane compositional changes.
