Changes in lipolysis and lipogenesis in selected tissues of the landlocked lamprey, Petromyzon marinus, during metamorphosis

This study was designed to examine the biochemical basis of lipid alterations in liver, kidney, and intestine of sea lamprey, Petromyzon marinus, during their nontrophic metamorphosis. Lipolysis, as indicated by triacylglycerol lipase (TGL) activity, increased in liver from larva to stage 6 and in kidney from stage 3 to stage 5, but declined in intestine from stage 3 to stage 5. Fatty acid synthesis and triacylglycerol synthesis were assessed by acetyl-CoA carboxylase (ACC) and diacylglycerol acyltransferase (DGAT) activities, respectively. Acetyl-CoA carboxylase activity decreased in kidney from larva to stage 6 and in liver from stage 3 to stage 6. Diacylglycerol acyltransferase activity in liver increased from larva to stage 5 and in intestine from stage 3 to stage 6, but it was unchanged in kidney. Oxidative metabolism, as estimated by citrate synthase (CS) activity, decreased in liver and intestine from larva to stage 6 and in kidney from larva to stage 3. These data indicate that changes in the activities of TGL, ACC, DGAT, and CS are development-dependent and tissue-specific and suggest that lamprey metamorphosis proceeds in two distinct metabolic phases. The first phase, displayed in larva and stage 3 of metamorphosis, is predominated by lipid depletion from intestine and lipid accumulation in liver and kidney, whereas the second phase, displayed in stage 3 to stage 6, is predominated by lipid depletion from liver and kidney and lipid accumulation in intestine. These biochemical changes may provide the energy required for the pronounced developmental reorganization that occurs during nontrophic metamorphosis of lamprey.