EFFECTS OF SOMATOSTATIN ON LIPID-METABOLISM OF LARVAE AND METAMORPHOSING LANDLOCKED SEA LAMPREY, PETROMYZON-MARINUS

This study was designed to examine the role of somatostatin in regulat ing changes in lipid metabolism of larvae and metamorphosing landlocke d sea lamprey, Petromyzon marinus. Larvae and animals in late metamorp hosis (stage 6 on a 7-stage scale) were injected intraperitoneally onc e per day for 2 days with either saline (0.6%) or somatostatin-14 (SS- 14; 500 ng/g body wt). Injection of SS-14 into larval and stage 6 meta morphosing animals resulted in elevated plasma fatty acids levels. In larvae, SS-14-induced hyperlipidemia was supported by enhanced lipolys is, as indicated by increased triacylglycerol lipase (TGL) activity in the liver and kidney. Mobilization of larval renal lipid was accompan ied by reduced TG synthesis, as indicated by decreased diacylglycerol acyltransferase (DGAT) activity. In stage 6 metamorphosing lamprey, SS -14 did not significantly affect TGL activity; however, SS-14 signific antly reduced fatty acid synthesis, as measured by acetyl-CoA carboxyl ase activity, in kidney, liver, and muscle, as well as muscular TG syn thesis. SS-14-stimulated lipid depletion is reminiscent of the pattern of lipid metabolism displayed by I! marinus during their spontaneous metamorphosis-an observation which suggests that somatostatin may play a role in metamorphosis-associated changes in lipid metabolism in thi s species. (C) 1998 Academic Press.