Phosphatidylinositol-specific phospholipase C releases lipoprotein lipase from the heparin releasable pool in rat heart cell cultures.
The effect of phosphatidylinositol-specific phospholipase C (PI-PLC) on the release of lipoprotein lipase was studied in F1 heart cell cultures. Exposure of the cultures for 10 min to PI-PLC resulted in a 2-fold increase in the release of lipoprotein lipase (LPL) into the culture medium. PI-PLC released LPL from the heparin-releasable pool and PI-PLC was not effective in cultures pretreated with heparin. Insulin had no influence on the release of LPL from the heart cell cultures, even though it enhanced the uptake of 2-deoxy[3H]glucose by these cells. In cultures labeled with 35S, treatment with PI-PLC resulted in an increase in the release of 35S-labeled proteoglycan. PI-PLC was also effective in enhancing the release of bovine LPL exogenously bound to cultured aortic smooth muscle cells. The findings that PI-PLC was not effective after heparin, that it did release exogenously added LPL to cell cultures and that it released 35S-labeled proteoglycan, were interpreted to indicate that PI-PLC apparently acts on the release of LPL in an indirect manner, releasing heparan sulphate to which LPL is bound. As there is a previously described correlation between circulating LPL and the heparin-releasable LPL, we hypothesize that the activity of PI-PLC in the endothelial cell membrane or plasma phosphatidyl-specific phospholipase D regulates the plasma LPL levels.
Chajek-Shaul
T
T
Department of Medicine B, Hadassah University Hospital, Jerusalem, Israel.
Halimi
O
O
Ben-Naim
M
M
Stein
O
O
Stein
Y
Y
D000818:Animals; D001011:Aorta; D003994:Bucladesine / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000378:metabolism; D006321:Heart / Q000187:drug effects; D006493:Heparin / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism* / Q000494:pharmacology; D011509:Proteoglycans / Q000378:metabolism; D051381:Rats
D007328:Insulin; D011509:Proteoglycans; D003994:Bucladesine; D006493:Heparin; D003847:Deoxyglucose; D008071:Lipoprotein Lipase; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase