Effects of MgATP on ATP utilization and force under normal and simulated ischaemic conditions in rat cardiac trabeculae

J. P. Ebus, Z. Papp, R. Zaremba, G. J.M. Stienen

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Abstract

The dependency of ATP utilization and isometric force on [MgATP] was studied in skinned rat trabeculae under normal (pH 7.0) and simulated ischaemic (pH 6.2, 30 mM added Pi) conditions at 20±1 °C. At saturating [Ca2+], mean (±SEM) ATP utilization at 5 mM MgATP (A0) was 0.48±0.03 mM/s and force (F0) was 37±2 kN/m2. At 10 μM MgATP under normal conditions ATP utilization decreased gradually to 66±3% of A0, and force increased to 169±7% of F0. Under ischaemic conditions at 10 μM MgATP, ATP utilization decreased from 30±5% to 11±2% of A0 whereas force increased eight-fold from 12±4% to 97±7% of F0. The [MgATP] at half-maximal ATP utilization (Km) under ischaemic conditions was 21±3 μM. At pH 7.0, Km was estimated to be less than 10 μM. These results show that tension cost decreases markedly with decreasing MgATP. Under ischaemic conditions parallel changes in Ca2+ sensitivity of force and ATP utilization were observed, corresponding to 1.3 pCa units. Reducing [MgATP] from 0.5 to 0.05 mM caused a modest reversal of this change in Ca2+ sensitivity. These changes in Ca2+ sensitivity are consistent with a marked reduction in active force and force-related ATP utilization during ischaemia but are insufficient to explain the ischaemic contracture on the basis of active force development.

Original languageEnglish
Pages (from-to)102-111
Number of pages10
JournalPflugers Archiv European Journal of Physiology
Volume443
Issue number1
DOIs
Publication statusPublished - Nov 29 2001

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Keywords

  • ATP
  • Adenosine triphosphatase
  • Cardiac muscle
  • Ischaemia

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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