Treatment of cardiac myocytes with 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, forskolin or cholera toxin does not stimulate cellular or heparin-releasable lipoprotein lipase activities.
Incubation of isolated cardiac myocytes with 500 microM-8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP) or 100 microM-forskolin for 2 1/2 h did not increase the heparin-induced release of lipoprotein lipase (LPL) into the medium. When LPL activity in cardiac myocytes was depleted by treatment of rats with cycloheximide (2 mg/kg; 2.5 h) and inclusion of the protein-synthesis inhibitor in the isolation solutions, incubation with CPT-cAMP or forskolin did not influence the rate of repletion of LPL activity in cells or the recovery of heparin-releasable LPL activity. Although the administration of cholera toxin (0.5 mg/kg; 16-17 h) to rats increased LPL activity in a low-speed supernatant fraction from heparin-perfused hearts, LPL activity was not increased in cardiac myocytes from cholera-toxin-treated rat hearts, and the heparin-induced release of LPL was unchanged. Incubation of cultured ventricular myocytes with 1 microgram of cholera toxin/ml or 500 microM-CPT-cAMP for 24 h did not increase cellular LPL activity or LPL released into the culture medium after a 40 min incubation with heparin. Therefore interventions that stimulate adenylate cyclase activity (forskolin, cholera toxin) or incubation with CPT-cAMP do not increase cellular LPL activity or promote the translocation of LPL to a heparin-releasable fraction in cardiac myocytes.
Carroll
R
R
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary, Alberta, Canada.
Juhasz
A
A
Severson
D L
DL
D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology*; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013873:Thionucleotides / Q000494:pharmacology*
D013873:Thionucleotides; D005576:Colforsin; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D006493:Heparin; D002772:Cholera Toxin; D003513:Cycloheximide; D000242:Cyclic AMP; D008071:Lipoprotein Lipase