Preferential in vivo accumulation of sn-2,3-diacylglycerols in postheparin plasma of rats

1977 ◽  
Vol 55 (10) ◽  
pp. 1075-1081 ◽  
Author(s):  
N. Morley ◽  
A. Kuksis ◽  
A. G. D. Hoffman ◽  
G. Kakis
Keyword(s):  
Portal Vein ◽  
Lipoprotein Lipase ◽  
Hepatic Lipase ◽  
Water Interface ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Oil Water ◽  
Hydrolysis Of

The stereochemical course of in vivo hydrolysis of triacylglycerols by lipoprotein lipase was investigated by determining the structure of diacylglycerol intermediates in postheparin plasma of rats which had been fed [3H]glycerol-labeled Intralipid 2 h before an injection of heparin or had been given an injection of a mixture of [3H]glycerol-Intralipid and heparin. During the clearance of both the natural chylomicrons and the artificial emulsion, sn-2,3-diacylglycerols (60–80%) were found to be the dominant enantiomers. Similar results were obtained when the contribution of the hepatic lipase was altered, either by tying off the mesentery artery and portal vein before injection of heparin, or by injection of heparin directly into the portal vein. These findings are consistent with a preferential release of the acyl group from the sn-1 position of the triacylglycerol molecule as demonstrated previously in vitro. A preferential orientation of the substrate in the enzyme–substrate complex or at the oil–water interface is discussed as a possible basis for these effects.

scholarly journals Lipolysis generates platelet dysfunction after in vivo heparin administration

2002 ◽  
Vol 103 (4) ◽  
pp. 433-440 ◽  
Author(s):  
Elijah W. MURIITHI ◽  
Philip R. BELCHER ◽  
Stephen P. DAY ◽  
Mubarak A. CHAUDHRY ◽  
Muriel J. CASLAKE ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Cardiopulmonary Bypass ◽  
Lipoprotein Lipase ◽  
Whole Blood ◽  
Ex Vivo ◽  
Hepatic Lipase ◽  
Platelet Factor 4 ◽  
Platelet Factor

Heparin, when administered to patients undergoing operations using cardiopulmonary bypass, induces plasma changes that gradually impair platelet macroaggregation, but heparinization of whole blood in vitro does not have this effect. The plasma changes induced by heparin in vivo continue to progress in whole blood ex vivo. Heparin releases several endothelial proteins, including lipoprotein lipase, hepatic lipase, platelet factor-4 and superoxide dismutase. These enzymes, which remain active in plasma ex vivo, may impair platelet macroaggregation after in vivo heparinization and during cardiopulmonary bypass. In the present study, proteins were added in vitro to hirudin (200units·ml-1)-anticoagulated blood from healthy volunteers, and the platelet macroaggregatory responses to ex vivo stimulation with collagen (0.6μg·ml-1) were assessed by whole-blood impedance aggregometry. Over a 4h period, human lipoprotein lipase and human hepatic lipase reduced the platelet macroaggregatory response from 17.0±2.3 to 1.5±1.3 and 1.2±0.6Ω respectively (means±S.D.) (both P<0.01; n = 6). Other lipoprotein lipases also impaired platelet macroaggregation, but platelet factor-4 and superoxide dismutase did not. Platelet macroaggregation showed an inverse linear correlation with plasma concentrations of non-esterified fatty acids (r2 = 0.69; two-sided P<0.0001; n = 8), suggesting that heparin-induced lipolysis inhibits platelet macroaggregation. Lipoprotein degradation products may cause this inhibition by interfering with eicosanoids and other lipid mediators of metabolism.

scholarly journals Effect of protamine on lipoprotein lipase and hepatic lipase in rats

1994 ◽  
Vol 304 (3) ◽  
pp. 959-966 ◽  
Author(s):  
M Hultin ◽  
G Olivecrona ◽  
T Olivecrona
Keyword(s):  
Endothelial Cell ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Binding Sites ◽  
Hepatic Lipase ◽  
Lipoprotein Lipase Activity ◽  
Cell Surfaces ◽  
Intravenous Injections

The polycation protamine impedes the catabolism of triglyceride-rich lipoproteins and this has been suggested to be due to intravascular inactivation of lipoprotein lipase. We have made intravenous injections of protamine to rats and found that both lipoprotein lipase and hepatic lipase activities were released to plasma. The effect of protamine was more short-lived than that obtained by injection of heparin. The release of hepatic lipase by protamine was as effective as the release by heparin, while the amount of lipoprotein lipase released by protamine was only about one-tenth of that released by heparin. This was not due to inactivation of lipoprotein lipase, since injection of an excess of heparin 10 min after injection of protamine released as much lipoprotein lipase activity to plasma as in controls. The results in vivo differed from those obtained in model experiments in vitro. Protamine was able to almost quantitatively release both lipoprotein lipase and hepatic lipase from columns of heparin-agarose. The displacement was dependent on the total amount of protamine that had passed over the column, indicating that it was due to occupation by protamine of all available binding sites. Our results in vivo showed that the binding sites for lipoprotein lipase were not blocked as efficiently as those for hepatic lipase, indicating that the binding structures were not identical. It was concluded that the impaired turnover of lipoproteins by protamine probably was due to prevention of binding of the lipoproteins to endothelial cell surfaces rather than to impaired lipase function.

Protection of α-amylase from proteolysis by adsorption to feed components in vitro and in the porcine small intestine

2018 ◽  
Vol 58 (4) ◽  
pp. 640
Author(s):  
Anton M. Pluschke ◽  
Paulus G. M. Jochems ◽  
Barbara A. Williams ◽  
Michael J. Gidley
Keyword(s):  
Small Intestine ◽  
Digestive Enzymes ◽  
Specific Binding ◽  
Wheat Starch ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Food Components ◽  
Small Intestinal

The interactions between digestive enzymes and non-substrate feed components, and the impacts these have on enzyme activity, have rarely been studied. The aim of the present study was to determine the ability of granular wheat starch and whole porcine diets to protect porcine pancreatic α-amylase from proteolysis by trypsin both in vitro and in vivo. Granular wheat starch protected α-amylase from degradation in vitro by adsorbing trypsin and reducing its proteolytic activity. This protection was also found for a complete pig diet and corresponded to undetectable soluble-trypsin activity in the presence of the diet. Pancreatic α-amylase from small intestinal digesta of pigs was active from the duodenum to the ileum (~200–330 U/mL) irrespective of the addition of a protease inhibitor immediately after sampling, most likely due to binding with other food components protecting it from proteolysis. We conclude that non-specific binding between pancreatic digestive enzymes and food components may be competitive with enzyme–substrate complex formation, and therefore important in determining differences in the rate of digestion of macronutrients along the small intestine.

Heparin

1985 ◽  
Vol 05 (03) ◽  
pp. 121-126
Author(s):  
L. B. Jaques
Keyword(s):  
Lipoprotein Lipase ◽  
Antithrombin Iii

ZusammenfassungIn vivo bewirkt Heparin das Auftreten einer Lipoprotein-Lipase, einer Diaminoxydase (Histaminase) und anderer Enzyme. In Tierversuchen konnten viele günstige Wirkungen von Heparin und Heparinoiden aufgezeigt werden, wie z.B. Schutzeffekte gegen toxische Medikamente und Prozeduren, gegen Überempfindlichkeitsreaktionen, Änderungen von Hormoneffekten und die Erhöhung der negativen elektrischen Ladung von Körperzellen. Die Einzelwirkungen sind für bestimmte Kettenstrukturen spezifisch. Während Heparin in vitro gerinnungshemmend wirksam ist, zeigt der Vergleich der gerinnungshemmenden Wirkung in der Blutzirkulation mit der chemischen Konzentration im Blut, daß in vivo eine Aktivierung von nicht gerinnungshemmend aktiven Fraktionen bzw. Heparinketten erfolgt. Heparin wird rasch von den Zellen des RES-Systems gegen einen Konzentrationsgradienten aufgenommen, so daß in vivo die Heparinkonzentration im Gefäßendothel lOOOfach höher ist als im Blut.Die Fixierung des Heparins im Endothel vermehrt das elektronegative Potential des Endothels. Diese Wirkung und andere Wirkungen (die Aktivierung von Antithrombin III etc.) sind lokal die Basis der thromboseverhütenden Heparinwirkung. Demnach ist das Endothel das Zielorgan für Heparin.

Autologous transplantation of mesenchymal stem cells into the portal vein of the miniature pig; a preliminary experiment for NOTES approach

2019 ◽  
Vol 98 (9) ◽  
pp. 350-355
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Cell Therapy ◽  
Portal Vein ◽  
Liver Parenchyma ◽  
Miniature Pig ◽  
Hepatic Diseases ◽  
Study Results

Introduction: There is evidence that mesenchymal stem cells (MSCs) could trans-differentiate into the liver cells in vitro and in vivo and thus may be used as an unfailing source for stem cell therapy of liver disease. Combination of MSCs (with or without their differentiation in vitro) and minimally invasive procedures as laparoscopy or Natural Orifice Transluminal Endoscopic Surgery (NOTES) represents a chance for many patients waiting for liver transplantation in vain. Methods: Over 30 millions of autologous MSCs at passage 3 were transplanted via the portal vein in an eight months old miniature pig. The deposition of transplanted cells in liver parenchyma was evaluated histologically and the trans-differential potential of CM-DiI labeled cells was assessed by expression of pig albumin using immunofluorescence. Results: Three weeks after transplantation we detected the labeled cells (solitary, small clusters) in all 10 samples (2 samples from each lobe) but no diffuse distribution in the samples. The localization of CM-DiI+ cells was predominantly observed around the portal triads. We also detected the localization of albumin signal in CM-DiI labeled cells. Conclusion: The study results showed that the autologous MSCs (without additional hepatic differentiation in vitro) transplantation through the portal vein led to successful infiltration of intact miniature pig liver parenchyma with detectable in vivo trans-differentiation. NOTES as well as other newly developed surgical approaches in combination with cell therapy seem to be very promising for the treatment of hepatic diseases in near future.

Studies on the mechanism of acute inhibition of thyroglobulin hydrolysis by iodine

1985 ◽  
Vol 108 (4) ◽  
pp. 511-517 ◽  
Author(s):  
Nandalal Bagchi ◽  
Birdie Shivers ◽  
Thomas R. Brown
Keyword(s):  
Time Course ◽  
Period 2 ◽  
Iodotyrosine Deiodinase ◽  
Rate Of Hydrolysis ◽  
Underlying Mechanisms ◽  
Excess Iodide ◽  
Sites Of Action ◽  
Hydrolysis Of

Abstract. Iodine in excess is known to acutely inhibit thyroidal secretion. In the present study we have characterized the time course of the iodine effect in vitro and investigated the underlying mechanisms. Labelled thyroid glands were cultured in vitro in medium containing mononitrotyrosine, an inhibitor of iodotyrosine deiodinase. The rate of hydrolysis of labelled thyroglobulin was measured as the proportion of labelled iodotyrosines and iodothyronines recovered at the end of culture and was used as an index of thyroidal secretion. Thyrotrophin (TSH) administered in vivo acutely stimulated the rate of thyroglobulin hydrolysis. Addition of Nal to the culture medium acutely inhibited both basal and TSH-stimulated thyroglobulin hydrolysis. The effect of iodide was demonstrable after 2 h, maximal after 6 h and was not reversible upon removal of iodide. Iodide abolished the dibutyryl cAMP induced stimulation of thyroglobulin hydrolysis. Iodide required organic binding of iodine for its effect but new protein or RNA synthesis was not necessary. The inhibitory effects of iodide and lysosomotrophic agents such as NH4C1 and chloroquin on thyroglobulin hydrolysis were additive suggesting different sites of action. Iodide added in vitro altered the distribution of label in prelabelled thyroglobulin in a way that suggested increased coupling in the thyroglobulin molecule. These data indicate that 1) the iodide effect occurs progressively over a 6 h period, 2) continued presence of iodide is not necessary once the inhibition is established, 3) iodide exerts its action primarily at a post cAMP, prelysosomal site and 4) the effect requires organic binding of iodine, but not new RNA or protein synthesis. Our data are consistent with the hypothesis that excess iodide acutely inhibits thyroglobulin hydrolysis by increasing the resistance of thyroglobulin to proteolytic degradation through increased iodination and coupling.

scholarly journals Catalytic activity and stereoselectivity of engineered phosphotriesterases towards structurally different nerve agents in vitro

2021 ◽  
Author(s):  
Anja Köhler ◽  
Benjamin Escher ◽  
Laura Job ◽  
Marianne Koller ◽  
Horst Thiermann ◽  
...  
Keyword(s):  
Plasma Clearance ◽  
Nerve Agents ◽  
Inhibition Assay ◽  
Ache Inhibition ◽  
Catalytic Activities ◽  
Chiral Lc ◽  
Hydrolysis Of ◽  
Medical Countermeasures

AbstractHighly toxic organophosphorus nerve agents, especially the extremely stable and persistent V-type agents such as VX, still pose a threat to the human population and require effective medical countermeasures. Engineered mutants of the Brevundimonas diminuta phosphotriesterase (BdPTE) exhibit enhanced catalytic activities and have demonstrated detoxification in animal models, however, substrate specificity and fast plasma clearance limit their medical applicability. To allow better assessment of their substrate profiles, we have thoroughly investigated the catalytic efficacies of five BdPTE mutants with 17 different nerve agents using an AChE inhibition assay. In addition, we studied one BdPTE version that was fused with structurally disordered PAS polypeptides to enable delayed plasma clearance and one bispecific BdPTE with broadened substrate spectrum composed of two functionally distinct subunits connected by a PAS linker. Measured kcat/KM values were as high as 6.5 and 1.5 × 108 M−1 min−1 with G- and V-agents, respectively. Furthermore, the stereoselective degradation of VX enantiomers by the PASylated BdPTE-4 and the bispecific BdPTE-7 were investigated by chiral LC–MS/MS, resulting in a several fold faster hydrolysis of the more toxic P(−) VX stereoisomer compared to P(+) VX. In conclusion, the newly developed enzymes BdPTE-4 and BdPTE-7 have shown high catalytic efficacy towards structurally different nerve agents and stereoselectivity towards the toxic P(−) VX enantiomer in vitro and offer promise for use as bioscavengers in vivo.

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