The Effects of the NMR Shift-reagents Dy(PPP)2, Dy(TTHA) and Tm(DOTP) on Developed Pressure in Isolated Perfused Rat Hearts. The Role of Shift-reagent Calcium Complexes

Balázs Gaszner, Tamás Simor, Gábor Hild, Gabriel A. Elgavish

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The 23Na NMR shift-reagent complexes (Dy(PPP)2. Dy(TTHA). and Tm(DOTP)) bind stoichiometric amounts of Ca2+. Thus, in perfused rat heart systems, a supplementation of Ca2+ is required to maintain the requisite extracellular free calcium concentration ([Cao]f) and to approximate a physiological level of contractile function. The amount of reagent-bound Ca2+ in a heart perfusate that contains a shift-reagent depends on: (1) Ca2+ binding by excess ligand used during the preparation of the shift-reagent; and (2) the Ca2+ binding affinity of the shift-reagent. To address point 1), we introduced a 1H and 31 NMR spectroscopic titration method to quantify directly the concentration of the excess ligand. We also used this method to minimize the amount of excess ligand (L) and thus the amount of Ca·L complex. To address point (2). we determined the stepwise Kd (μM) values of the Ca complexes of the three shift-reagents·: Dy(PPP)2, Kd1, =0.09. Kd2= 7.9: Dy(TTHA), Kd1 = 10.66. Kd2= 10.12: and Tm(DOTP). Kd1 =0.502. Kd2 = 4.98. The Kd values of the Ca complexes of the phosphonate and triphosphate based shift-reagents, Tm(DOTP) and Dy(PPP)2, respectively, are lower than those of the polyaminocarboxylate-based Dy(TTHA), indicating stronger Ca binding affinities for the former two types of complexes. We have also shown a positive correlation between [Cao]f and left ventricular developed pressure (LVDP) in perfused rat hearts. Dy(TTHA) has shown no effect on LVDP v [Cao]f. The LVDP values in the presence of the phȯsphonate and triphosphate based shift-reagents. however, were significantly higher than expected from the [Cao]f levels alone. Thus a positive inotropic effect. independent of [Cao]f, is evident in the presence of Tm(DOTP) or Dy(PPP)2.

Original languageEnglish
Pages (from-to)1945-1956
Number of pages12
JournalJournal of Molecular and Cellular Cardiology
Volume33
Issue number11
DOIs
Publication statusPublished - Jan 1 2001

Keywords

  • Isolated perfused rat hearts
  • NMR shift-reagents
  • Positive inotropy
  • Positive modulators
  • Shift-reagent calcium complexes

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

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