Glucagon and insulin regulate lipolysis in trout liver by altering phosphorylation of triacylglycerol lipase

J. S. Harmon, L. M. Rieniets, M. A. Sheridan

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Rainbow trout were used to investigate the hormonal regulation by glucagon and insulin of hepatic triacylglycerol (TG) lipase activation. Two purified preparations of the trout hepatic TG lipase enzyme, the 110,000-g preparation and the resuspended ammonium sulfate fraction (ASF), were activated up to 58% with (in mM) 0.5 ATP, 0.01 cAMP, 5 MgCl2, and exogenous protein kinase over control levels. ATP or cAMP alone had no effect on activation. Activation of the trout hepatic lipase was reversible; complete inactivation of the ASF was obtained within 3 h in the presence of exogenous phosphorylase phosphatase. Adenosine 3',5'-cyclic monophosphate (cAMP)/ATP-dependent 32P- phosphorylation of trout hepatic lipase was observed within 5 min of incubation with the cAMP/ATP-Mg2+ activation system and 25 μCi [32P]ATP. Hormonal modulation of trout hepatic lipase phosphorylation was studied in isolated hepatocytes. Hepatocytes were incubated with [32P]monopotassium phosphate for 3 h, then exposed to mammalian glucagon (GLU). Within 5 min, increased lipolysis was accompanied by a 95% increase in phosphorylation of the enzyme. Mammalian insulin (INS) depressed GLU-stimulated phosphorylation by 56% and inhibited GLU-stimulated lipolysis. These results indicate that GLU and INS modulate lipolysis in trout liver by altering phosphorylation of the TG lipase enzyme.

Original languageEnglish
Pages (from-to)R255-R260
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume265
Issue number1 34-1
DOIs
StatePublished - 1993

Keywords

  • glucagon
  • insulin
  • lipolysis

Fingerprint

Dive into the research topics of 'Glucagon and insulin regulate lipolysis in trout liver by altering phosphorylation of triacylglycerol lipase'. Together they form a unique fingerprint.

Cite this