Metabolic and Biochemical Correlates of Thermal Acclimation in the Rough-Skinned Newt Taricha granulosa

Abstract

Taricha granulosa (the rough-skinned newt) exhibited no thermal acclimation of metabolism when measured at a low experimental temperature (ET) (5 C) but underwent pronounced acclimation at a high ET (20 C). Thermal acclimation markedly altered the substrate concentration at which enzyme activity was 50% of maximum activity ($K_{s}$) for two enzymes, lactate dehydrogenase (LDH) and malate dehydrogenase (MDH). In general, the $K_{s}$ decreased after acclimation to low temperatures. Maximum activity of both enzymes, by contrast, was unaffected by thermal acclimation. No qualitative differences in isozymes from warm-and cold-acclimated salamanders were evident from starch gel electrophoresis of LDH, MDH, or IDH (isocitrate dehydrogenase). Acclimation to cold temperatures had no effect on the proportions of most phospholipids in the liver but increased the proportions of unsaturated fatty acids and decreased sphingomyelin content. In most respects, Taricha granulosa resembled other ectothermic vertebrates in i...