Erratum: Endothelial binding sites for lipoprotein lipase are not diminished in perfused hearts from diabetic rats

1998 ◽  
Vol 76 (2) ◽  
pp. 242
Author(s):  
Limin Liu ◽  
David L Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Binding Sites ◽  
Bovine Milk ◽  
High Capacity ◽  
Progressive Increase ◽  
Diabetic Rats ◽  
Coronary Vasculature ◽  
Rat Hearts ◽  
Perfused Hearts

This article was published with the wrong French abstract. The correct English and French abstracts are printed below in full. The Publisher regrets this error. Abstract : The possibility that diabetes reduces functional, heparin-releasable lipoprotein lipase (HR-LPL) activity on the coronary vasculature of perfused hearts by altering endothelial binding sites for the enzyme was examined by measuring the binding and subsequent heparin-induced release of exogenous lipoprotein lipase purified from bovine milk (mLPL). Rat hearts were first perfused with heparin (5 U/mL) for 5 min to displace endogenous HR-LPL into the perfusate. The subsequent perfusion of control hearts with 0.05-2 µg/mL mLPL resulted in a progressive increase in bound exogenous exzyme that could be released by a second heparin perfusion. Induction of an acute, insulin-deficient model of diabetes (100 mg/kg streptozotocin 4-5 days prior to heart perfusions) reduced endogenous HR-LPL activity, but the binding and heparin-induced release of mLPL (0.5 µg/mL) were the same as measured in control hearts. Therefore, diabetes does not alter low-affinity, high-capacity proteoglycan binding sites for mLPL on the endothelium of perfused hearts.Key words: diabetes, lipoprotein lipase, perfused hearts.

Myocardial lipoprotein lipase activity: regulation by diabetes and fructose-induced hypertriglyceridemia

1995 ◽  
Vol 73 (3) ◽  
pp. 369-377 ◽  
Author(s):  
Limin Liu ◽  
David L. Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Selective Reduction ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Compensatory Response ◽  
Perfusion Solution ◽  
Rat Hearts ◽  
Perfused Hearts ◽  
Control Plasma ◽  
Sustained Increase

The decrease in myocardial lipoprotein lipase (LPL) activity observed previously in acute, severe models of insulin-deficient diabetes may be a compensatory response to hypertriglyceridemia and a sustained increase in fatty acid delivery to cardiomyocytes. The administration of fructose (10% solution in the drinking water for 4 days) to rats produced hypertriglyceridemia, but heparin-releasable LPL activity from perfused hearts and total and heparin-releasable LPL activities in isolated cardiomyocytes were not reduced. The acute (4 day) induction of a mild diabetic state (60 mg/kg streptozotocin) resulted in modest hypertriglyceridemia, and a selective decrease in heparin-releasable LPL activity in perfused hearts; LPL activity in cardiomyocytes from diabetic rat hearts was not reduced. Therefore, the diabetes-induced fall in myocardial LPL activity is not secondary to hypertriglyceridemia, since fructose treatment did not change LPL activity. Perfusion of rat hearts with 100 μM lysophosphatidylcholine (LPC) released a small amount of LPL activity into the perfusate, but only if albumin was omitted from the perfusion solution. Thus, the selective reduction in heparin-releasable LPL activity in perfused diabetic hearts is probably not the consequence of displacement by LPC, a lipolytic product of the LPL-catalyzed degradation of triacylglycerol-rich lipoproteins. Circulating LPL activity in the plasma of diabetic rats was not decreased relative to control plasma enzyme activity; therefore, the reduction in heparin-releasable LPL activity is not because circulating LPL was less available for uptake by the endothelium in diabetic hearts.Key words: diabetes, lipoprotein lipase, perfused hearts, cardiomyocytes.

scholarly journals Decrease in cardiac phosphatidylglycerol in streptozotocin-induced diabetic rats does not affect cardiolipin biosynthesis: evidence for distinct pools of phosphatidylglycerol in the heart

1995 ◽  
Vol 306 (3) ◽  
pp. 759-764 ◽  
Author(s):  
G M Hatch ◽  
S G Cao ◽  
A Angel
Keyword(s):  
Rat Heart ◽  
Specific Radioactivity ◽  
Fold Increase ◽  
Mitochondrial Fraction ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Rat Hearts ◽  
Perfused Hearts ◽  
Continuous Pulse ◽  
Pool Sizes

Biosynthesis of phosphatidylglycerol (PG) and cardiolipin (CL) were investigated in perfused hearts of diabetic rats 4 days or 28 days after streptozotocin injection. Sham-injected and insulin-treated diabetic rats were used as controls. In addition, another group of rats fasted for 54 h was examined. Isolated rat hearts from these groups were perfused for 30 min with [32P]P(i), and the radioactivity incorporated into PG and CL and their pool sizes were determined in heart ventricles. There was no difference in the amount of radioactivity incorporated into CL, PG or other phospholipids between all groups. In addition, the pool sizes of CL and other phospholipids were unaltered. However, a striking decrease in the pool size of PG was observed in both diabetic and fasted rats compared to sham- and insulin-treated controls at 4 days after streptozotocin injection. The decrease in PG mass in diabetic rats was rapid (within 24-48 h) and was localized to cardiac membranes. Diabetes did not affect the activity of the enzymes of PG and CL biosynthesis in the mitochondrial fraction, or phospholipase A activity in subcellular fractions prepared from rat heart homogenates. In addition, pulse-chase experiments confirmed that diabetes did not affect the rate of new PG or CL biosynthesis. Since radioactivity associated with PG was unaltered in continuous-pulse perfusion experiments, a calculated 1.8-fold increase in the specific radioactivity of cardiac PG was observed in the hearts of acute diabetic rats compared with controls. Since the radioactivity incorporated into PG and CL, and the rate of CL biosynthesis, were unaltered in diabetic-rat hearts compared with controls, new CL was probably synthesized from newly synthesized PG. We postulate the existence of distinct pools of PG in the heart, and that the pool of newly synthesized PG used for CL biosynthesis does not appear to mix immediately with the pre-existing pool of PG in the isolated intact rat heart.

Diabetes reduces heparin- and phospholipase C-releasable lipoprotein lipase from cardiomyocytes

1991 ◽  
Vol 260 (3) ◽  
pp. E477-E485 ◽  
Author(s):  
J. E. Braun ◽  
D. L. Severson
Keyword(s):  
Cell Surface ◽  
Phospholipase C ◽  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Myocardial Cell ◽  
Diabetic Rats ◽  
Capillary Endothelium ◽  
Rat Hearts ◽  
Isolated Cardiac Myocytes ◽  
Covalently Linked

Incubation of isolated cardiac myocytes from rat hearts with heparin or phosphatidylinositol-specific phospholipase C (PLC) resulted in the release of lipoprotein lipase (LPL) into the medium. The release of LPL by the combination of heparin and PLC was not additive, and preincubation of cardiac myocytes with heparin eliminated the release of LPL in a subsequent incubation with PLC. This evidence suggests that LPL may be bound ionically to heparan sulfate proteoglycans that are covalently linked to the cell surface of cardiac myocytes by a phosphatidylinositol-glycan membrane anchor; a second pool of LPL may also be bound to proteoglycans attached directly to the myocardial cell surface. The induction of diabetes by the administration of streptozotocin (100 mg/kg for 3-4 days) to rats resulted in a decrease in the initial cellular activity of LPL and a marked reduction in the heparin-induced secretion of LPL into the medium of cardiac myocytes. The intravenous administration of insulin (5 U for 1 h) in diabetic rats reversed the effects of diabetes on cellular and heparin-releasable LPL activities. Diabetes also reduced the PLC-induced release of LPL. The reduction in the release of LPL from diabetic cardiac myocytes could result in a decrease in functional LPL activity at the capillary endothelium of whole hearts.

Regulation of myocardial lipoprotein lipase activity by diabetes and thyroid hormones

1994 ◽  
Vol 72 (11) ◽  
pp. 1259-1264 ◽  
Author(s):  
Limin Liu ◽  
David L. Severson
Keyword(s):  
Thyroid Hormones ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Hormone Treatment ◽  
Diabetic Rats ◽  
Lipoprotein Lipase Activity ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Perfused Hearts

Administration of streptozotocin (100 mg/kg) to adult Sprague–Dawley rats reduced both functional (heparin releasable) lipoprotein lipase activity in perfused hearts and total and heparin-releasable lipoprotein lipase activity in isolated cardio-myocytes, and produced a hypothyroid state (decreased plasma levels of triiodothyronine and thyroxine). Administration of replacement doses of triiodothyronine (3 or 10 μg/kg for 3 days) to diabetic rats normalized heparin-releasable lipoprotein lipase activity in perfused hearts, but the depressed lipoprotein lipase activity in cardiomyocytes from diabetic hearts was unchanged by in vivo thyroid hormone treatment. However, hypothyroidism in thyroidectomized rats did not alter lipoprotein lipase activity in either perfused hearts or isolated cardiomyocytes. Therefore, thyroid hormones may interact with some other factor(s) in this acute, insulin-deficient model of diabetes to selectively regulate functional, heparin-releasable lipoprotein lipase activity in perfused hearts.Key words: diabetes, hypothyroidism, lipoprotein lipase, perfused hearts, cardiomyocytes.

scholarly journals The effects of lactate, acetate, glucose, insulin, starvation and alloxan-diabetes on protein synthesis in perfused rat hearts

1986 ◽  
Vol 236 (2) ◽  
pp. 543-547 ◽  
Author(s):  
D M Smith ◽  
S J Fuller ◽  
P H Sugden
Keyword(s):  
Protein Synthesis ◽  
Time Course ◽  
Diabetic Rats ◽  
Perfused Heart ◽  
Translational Activity ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Percentage Basis ◽  
Perfused Hearts ◽  
Stimulation Of

Compared with glucose, lactate + acetate stimulated ventricular protein synthesis in anterogradely perfused hearts from fed or 72 h-starved rats. Stimulation was greater on a percentage basis in starved rats. Atrial protein synthesis was not detectably stimulated by lactate + acetate. Insulin stimulated protein synthesis in atria and ventricles. The stimulation of protein synthesis by lactate + acetate and insulin was not additive, the percentage stimulation by insulin being less in the ventricles of lactate + acetate-perfused hearts than in glucose-perfused hearts. Perfusion of hearts from 72 h-starved or alloxan-diabetic rats with glucose + lactate + acetate + insulin did not increase protein-synthesis rates or efficiencies (protein synthesis expressed relative to total RNA) to values for fed rats, implying there is a decrease in translational activity in these hearts. In the perfused heart, inhibition of protein synthesis by starvation and its reversal by re-feeding followed a relatively prolonged time course. Synthesis was still decreasing after 3 days of starvation and did not return to normal until after 2 days of re-feeding.

Sites of Insulin Action Using Ferritin Labeling

1971 ◽  
Vol 29 ◽  
pp. 540-541
Author(s):  
Burton B. Silver ◽  
Ronald S. Nelson
Keyword(s):  
Electron Microscopy ◽  
Binding Sites ◽  
Anterior Pituitary ◽  
Insulin Action ◽  
Diabetic Rats ◽  
Insulin Antibody ◽  
Fat Pad ◽  
Target Organs ◽  
Uranium Salts ◽  
Sugar Levels

Some investigators feel that insulin does not enter cells but exerts its influence in some manner on the cell surface. Ferritin labeling of insulin and insulin antibody was used to determine if binding sites of insulin to specific target organs could be seen with electron microscopy.Alloxanized rats were considered diabetic if blood sugar levels were in excess of 300 mg %. Test reagents included ferritin, ferritin labeled insulin, and ferritin labeled insulin antibody. Target organs examined were were diaphragm, kidney, gastrocnemius, fat pad, liver and anterior pituitary. Reagents were administered through the left common carotid. Survival time was at least one hour in test animals. Tissue incubation studies were also done in normal as well as diabetic rats. Specimens were fixed in gluteraldehyde and osmium followed by staining with lead and uranium salts. Some tissues were not stained.

Receptor Mediated Binding of the Fibrinolytic Components, Plasminogen and Urokinase, to Peripheral Blood Cells

1987 ◽  
Vol 58 (03) ◽  
pp. 936-942 ◽  
Author(s):  
Lindsey A Miles ◽  
Edward F Plow
Keyword(s):  
T Cells ◽  
B Cell ◽  
Peripheral Blood ◽  
Binding Sites ◽  
Blood Cells ◽  
High Capacity ◽  
Red Cells ◽  
Peripheral Blood Cells ◽  
Cellular Functions ◽  
Fibrinolytic Proteins

SummaryGlu-plasminogen binds to platelets; the monocytoid line, U937, and the human fetal fibroblast line, GM1380 bind both plasminogen and its activator, urokinase. This study assesses the interaction of these fibrinolytic proteins with circulating human blood cells. Plasminogen bound minimally to red cells but bound saturably and reversibly to monocytes, granulocytes and lymphocytes with apparent Kd values of 0.9-1.4 μM. The interactions were of high capacity with 1.6 to 49 × 105 sites/cell and involved the lysine binding sites of plasminogen. Both T cells and non-rosetting lymphocytes and two B cell lines saturably bound plasminogen. Urokinase bound saturably to gianulocytes, monocytes, non-rosetting lymphocytes and a B cell line, but minimally to T cells, platelets and red cells. Therefore, plasminogen binding sites of high capacity, of similar affinities, and with common recognition specificities are expressed by many peripheral blood cells. Urokinase receptors are also widely distributed, but less so than plasminogen binding sites. The binding ol plasminogen and/ or urokinase to these cells may lead to generation of cell- associated proteolytic activity which contributes to a variety of cellular functions.

Abnormal Platelet Serotonin Uptake and Binding Sites in Myeloproliferative Disorders

1984 ◽  
Vol 51 (03) ◽  
pp. 349-353 ◽  
Author(s):  
C Caranobe ◽  
P Sié ◽  
F Fernandez ◽  
J Pris ◽  
S Moatti ◽  
...  
Keyword(s):  
Binding Sites ◽  
High Capacity ◽  
Specific Inhibitor ◽  
Myeloproliferative Disorders ◽  
Normal Subjects ◽  
Binding Data ◽  
Full Explanation ◽  
Number Of Binding Sites ◽  
5 Ht Uptake ◽  
Kinetics Of

SummaryA simultaneous investigation of the kinetics of serotonin (5 HT) uptake and of binding sites was carried out in the platelets of normal subjects and of 10 patients affected with various types of myeloproliferative disorders (MD). The 5 HT uptake was analysed according to the Lineweaver-Burk and the Eadie-Hofstee methods. With the two methods, the patient’s platelets exhibited a dramatic reduction of the Vi max and of the Km; in some patients the Eadie-Hofstee analysis revealed that a passive diffusion phenomenon is superimposed on the active 5 HT uptake at least for the higher concentration used. The binding data were analysed with the Scatchard method. Two classes of binding sites (high affinity - low capacity, low affinity - high capacity) were found in normal subjects and patients. Pharmacological studies with imipramine, a specific inhibitor of 5 HT uptake, suggested that both the sites are involved in 5 HT uptake. The number of both binding sites was significantly decreased in patient’s platelets while the affinity constants of these binding sites were not significantly reduced in comparison with those of the control subjects. No correlations were found between Vi max, Km and the number of binding sites. These results suggest that a reduction in the number of platelet membrane acceptors for 5 HT commonly occurs in myeloproliferative disorders but does not provide a full explanation of the uptake defect.

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