1996 Fiscal Year Final Research Report Summary
Effects of anoxia and reoxygenation on intracellular Ca kinetics via Na/Ca exchanger in mammalian cardiomyocytes.
| Project/Area Number |
07670812
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | The Jikei University School of Medicine |
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Principal Investigator |
SEKI Shingo Jikei University School of Medicine, Dpt.Medicine 4 Lecturer, 医学部, 講師 (70179323)
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| Project Period (FY) |
1995 – 1996
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| Keywords | anoxia / calcium / fura-2 / ischemia / reperfusion / sodium calcium exchanger |
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| Research Abstract |
OBJECTIVE : We investigated the effects of anoxia and reoxygenation on intracellular Ca^<2+> regulation. The effects of anoxia on Ca^<2+> in myocytes were compared with those of ischemia and reperfusion in isolated perfused hearts.
METHODS : Single, enzymatically isolated guinea pig ventricular myocytes were exposed to 3-min of chemical anoxia with glucose-free Tyrode solution containing 1mM sodium dithionite and were reoxygenated for 10 min. The myocytes were exposed to rapid application of 10mM caffeine (Experiment A). The myocytes were also exposed to rapid cooling (RC) from 22ﾟC to 1ﾟC and rewarmed in Na^+-free solution (Experiment B). These procedures were performed during control, anoxia and reoxygenation. Intracellular Ca^<2+> concentration ([Ca^<2+>]i) was measured ratiometrically using indo-1 with simultaneous measurement of cell length. Isolated hearts from Sprague-Dawley rats were perfused by Langendorff's technique and [Ca^<2+>] i were measured using fura-2. Ischemia was ind
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uced by reduction of coronary flow to 10% of control for 10 min (Experiment C).
RESULTS : Experiment A.The amplitude of electrically stimulated and caffeine-evoked Ca^<2+> transients decreased during anoxia and recovered after reoxygenation. Diastolic [Ca^<2+>] i level elevated during anoxia and remained at this higher level on reoxygenation. Anoxia slowed the time to peak, and the time to 50%, 90% relaxation of the Ca^<2+> transient. The decline of indo-1 fluorescence on caffeine application was slowed during anoxia and partially recovered after reoxygenation. Experiment B.The amplitude of RC induced Ca^<2+> transient also decreased during anoxia and recovered after reoxygenation. The time to 50% and 90% relaxation of Ca^<2+> on rewarming were slowed during anoxia. Experiment C.The changes in amplitude of Ca^<2+> trnasient and diastolic [Ca^<2+>] i during ischemia were consistent with those of myocytes.
CONCLUSIONS : The forward mode of Na/Ca exchanger and the SR Ca^<2+> reuptake may be compromised during anoxia. Less
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