In memoriam Professor Dr. Dr. Ivar Trautschold f+3i. i. 1984)Stunmary: The mechanisrn of enzyme release from Lwigendoiff-periused rat heans was studied uader the injury condiuons of the Ca 2~ paradox and 2.4-dinnrophenol poisonirlg. During perftisioa wiih Krehs-Rfcger bufFer or in buffered sncrose sarcoplasmic enzymes were massnrely released when Ca-~ was reintroduced to the perfiision medium (Ca 2~ paradox). Mitochondrial matrix enzymes were released to a verv small exteot. Only the cytoplasmic isoen^me of the bilocular enzjine malaie deh}*drogenase \\-as released. The release kinetics of various enzymes with greath' differing molecular weights showed no significant diflferences. Qiialitatively the same results were obtained under 2,4-dinitrophenol poisoned condilions in Ca-~-free sucrose media. Sarcoplasmic enzymes were massively released, mitochondrial enz\Tnes did not appear in the perfusate. 2,4-Dinitrophenol poisoning alone was not sufficient to cause enz>me release. An additional swelling under these condilions w r as necessary. ATP from the extracellular space was able to enhance the enzjuie release, wfaich was brou^it about by 2 ? 4-dinitrophenol and cell swelling.A hypothesis is presented that enzyme rdease is produoed by initiaiing a membrane blebbing prooess. An devated intracellular Ca 2^ concentration is a necessary prerequisite. In the presence of ATP, acri\*e merabrane blebbing is catised by contractions of the membrane-anchored cjtoskeleton. In the absence of ATP passive membrane blebbing is induced by cell swelling, provided that the cytoskeleton has been cfosslinked by Ca 2^. Im Rahmen einer Hypothese wird der Mechanismus des'Enzymaustritts als "membrane blebbmg"~Prozeß dargestellt· Als notwendige Voraussetzung muß die intrazelluläre Ca 2 +-Konzentration erhöht sein. In Gegenwart von ATP wird ein aktives "membrane blebbing" durch Kontraktionen des membranverankerten Zytoskeletts verursacht. Ist kein ATP vorhanden, kann ein passives "membrane blebbmg" durch Schwellung ausgelöst werden, wenn das Zytoskelett vorher durch Ca 2 + vernetzt worden ist. Enzymaustrin am perfundierten Ratteniierzen: Die Funktionen des Zytoskeletts unter zellpathölogischen Bedingungen
Summary:Human, dog and rat erythrocytes were separated by centrifugation on a discontinuous buffered Percoll gradient into fractions of progressively increasing mean cell age to measure the in vivo decline in catalytic activity of eleven enzymes during the erythrocyte lifespan. Erythrocyte enzymes decline exponentially at different rates and also differ between the species. The maximal and minimal catalytic activities (erythrocyte catalytic activity at the beginning and at the end of the appröpriate erythrocyte life-span for a given species) and the intracellular half-life of enzymes were estimated. To test the hypothesis that circulating erythrocytes inake a significant contribution to the normal catalytic activity in plasma it was assumed äs a working hypothesis that the measured loss of catalytic activity in ageing erythrocytes is equivalent to the amount of the enzymes released in catalytically active form into plasma. This contribution was calculated. Die Abnahme der katalytischen Enzymaktivitätskonzentration von in vivo alternden Erythrocyten bei Mensch, Hund und Ratte Versuch der Begründung einer quantitativen Diagnostischen Enzymologie, IV.Zusammenfassung: Erythrocyten von Mensch, Hund und Ratte wurden in einem diskontinuierlichen PercollGradienten in Puffer in Fraktionen zunehmenden Alters separiert, um den in vivo-Abfall der katalytischen Aktivität von 11 Enzymen über die entsprechende Erythrocyten-Lebensdauer zu bestimmen. Die einzelnen Enzyme verlieren ihre kätalytische Aktivität exponentiell .mit unterschiedlicher Rate, auch unterschiedlich bei den untersuchten Spezies. Die maximalen und minimalen katalytischen Aktivitäten (kätalytische Aktivität der Erythrocyten zu Beginn und zum Ende der entsprechenden Erythrocyten-Lebensdauer der untersuchten Spezies) und die intrazelluläre Halbwertszeit der Enzyme wurden bestimmt. Um die Hypothese zu testen, daß zirkulierende Erythrocyten einen wesentlichen Beitrag zur normalen katalytischen Enzymaktivität des Plasmas leisten, wird als Arbeitshypothese angenommen, daß der Verlust des alternden Erythrocyten an katalytischer Aktivität gleichbedeutend ist mit einer Freisetzung an katalytisch aktivem Enzym in das Plasma. Dieser Beitrag wird berechnet.
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