scholarly journals Short-term incubation of cardiac myocytes with isoprenaline has no effect on heparin-releasable or cellular lipoprotein lipase activity

1987 ◽  
Vol 248 (1) ◽  
pp. 289-292 ◽  
Author(s):  
D L Severson ◽  
R Carroll ◽  
A Kryski ◽  
I Ramírez
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Lipase Activity ◽  
Incubation Medium ◽  
Activity Ratio ◽  
Lipoprotein Lipase Activity ◽  
Short Term ◽  
Cyclic Monophosphate

Heparin (5 units/ml) produced a rapid (5-10 min) release of lipoprotein lipase (LPL) into the incubation medium of cardiac myocytes. Preincubation of myocytes for 30 min with 0.01-10 microM-isoprenaline, 100 microM-forskolin or 500 microM-8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate did not increase heparin-releasable LPL activity. Incubation with isoprenaline also did not change cellular LPL activity, even though the catecholamine did increase the phosphorylase a activity ratio.

Regulation of lipoprotein lipase activity in cardiac myocytes from control and diabetic rat hearts by plasma lipids

1992 ◽  
Vol 70 (9) ◽  
pp. 1271-1279 ◽  
Author(s):  
Brian Rodrigues ◽  
Janice E. A. Braun ◽  
Michael Spooner ◽  
David L. Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Lipase Activity ◽  
Plasma Lipids ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Lipoprotein Lipase Activity ◽  
Triton Wr 1339 ◽  
Plasma Triacylglycerol

The objective of this investigation was to test the hypothesis that the diabetes-induced reduction in lipoprotein lipase activity in cardiac myocytes may be due to hypertriglyceridemia. Administration of 4-aminopyrazolopyrimidine (50 mg/kg) to control rats for 24 h reduced plasma triacylglycerol levels and increased the heparin-induced release of lipoprotein lipase into the incubation medium of cardiac myocytes. The acute (3–5 days) induction of diabetes by streptozotocin (100 mg/kg) produced hypertriglyceridemia and reduced heparin-releasable lipoprotein lipase activity in cardiac myocytes. Treatment of diabetic rats with 4-aminopyrazolopyrimidine resulted in a fall in plasma triacylglycerol content and increased heparin-releasable lipoprotein lipase activity. Administration of Triton WR-1339 also resulted in hypertriglyceridemia, but the heparin-induced release of lipoprotein lipase from control cardiac myocytes was not reduced in the absence of lipolysis of triacylglycerol-rich lipoproteins. Treatment with Triton WR-1339 did, however, increase the heparin-induced release of lipoprotein lipase from diabetic cardiac myocytes. Preparation of cardiac myocytes with 0.9 mM oleic acid resulted in a decrease in both total cellular and heparin-releasable lipoprotein lipase activities. These results suggest that the diabetes-induced reduction in heart lipoprotein lipase activity may, at least in part, be due to an inhibitory effect of free fatty acids, derived either from lipoprotein degradation or from adipose tissue lipolysis, on lipoprotein lipase activity in (and (or) release from) cardiac myocytes.Key words: diabetes, plasma triacylglycerols, cardiac myocytes, lipoprotein lipase.

Comparative effects of insulin and isoproterenol on lipoprotein lipase in rat adipose cells

1996 ◽  
Vol 270 (5) ◽  
pp. C1461-C1467 ◽  
Author(s):  
G. E. Chiappe de Cingalani ◽  
J. W. Goers ◽  
M. Giannotti ◽  
C. I. Caldiz
Keyword(s):  
Enzyme Activity ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Incubation Medium ◽  
Cell Membranes ◽  
Lipoprotein Lipase Activity ◽  
Rat Adipocytes ◽  
Enzyme Degradation ◽  
Cell Incubation ◽  
Adipose Cells

The effects of insulin and isoproterenol on lipoprotein lipase mass and enzyme activity were investigated in rat adipocytes. Cells were pulse labeled for 1 h with [35S]methionine to measure immunoprecipitable lipoprotein lipase. The results showed that 80% of the newly synthesized enzyme was membrane associated and 20% was secreted into the cell incubation medium. Enzyme activity was mainly associated with lipoprotein lipase secreted into the medium. A 10-min incubation with 10(-7) M insulin stimulated the secretion of lipoprotein lipase activity and the activity associated with adipocyte membranes. Conversely, 10(-6) M isoproterenol decreased the activity in all fractions. In addition, insulin increased lipoprotein lipase mass associated with cell membranes and decreased that in the incubation medium, whereas isoproterenol induced a decrease in both cell membranes and medium. Insulin and isoproterenol stimulated phosphorylation of lipoprotein lipase. These findings suggest that insulin stimulates the secretion of active lipoprotein lipase and a reuptake of inactive secreted enzyme, and isoproterenol decreases the activity by enzyme degradation. Moreover, because both agents stimulate phosphorylation of lipoprotein lipase, phosphorylation may play a role in the effect of insulin increasing enzyme activity, in secretion or reuptake, and in the effect of isoproterenol inducing degradation of lipoprotein lipase.

Acute diabetes does not reduce heparin-releasable lipoprotein lipase activity in perfused hearts from Wistar–Kyoto rats

1993 ◽  
Vol 71 (9) ◽  
pp. 657-661 ◽  
Author(s):  
Brian Rodrigues ◽  
David L. Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Lipase Activity ◽  
Cardiac Myocyte ◽  
Plasma Concentrations ◽  
Lipoprotein Lipase Activity ◽  
Sprague Dawley ◽  
Wistar Kyoto Rats ◽  
Wistar Kyoto ◽  
Perfused Hearts

The induction of diabetes (3–5 days duration) in Wistar–Kyoto rats by the administration of streptozotocin (100 mg/kg) did not increase plasma concentrations of triacylglycerols or free fatty acids, and did not reduce heparin-releasable (functional) lipoprotein lipase activity in perfused hearts. By comparison, diabetic Sprague–Dawley rats were characterized as having hypertriglyceridemia and decreased heparin-releasable lipoprotein lipase activity in perfused hearts. Therefore, the diabetes-induced reduction in myocardial lipoprotein lipase activity in Sprague–Dawley rat hearts may, at least in part, be a compensatory response to the hypertriglyceridemia and increased fatty acid delivery to the myocardial cell, which is a characteristic feature of most severe, insulin-deficient models of diabetes mellitus. Although functional, endothelium-bound lipoprotein lipase activity was not reduced in diabetic perfused hearts from Wistar–Kyoto rats, cellular and heparin-releasable lipoprotein lipase activity was reduced in cardiac myocyte preparations, suggesting that other mechanisms in addition to plasma triacylglycerol must regulate lipoprotein lipase activity in the whole diabetic Wistar–Kyoto rat heart and that cardiac myocytes may not be the exclusive source of functional lipoprotein lipase in the diabetic myocardium.Key words: diabetes, hypertriglyceridemia, lipoprotein lipase, perfused hearts, cardiac myocytes.

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