Excitation-contraction (E-C) coupling was investigated in rat hearts
6 wk after induction of myocardial infarction (MI) by ligation
of the left coronary artery. Heart weight was increased by 74\% and
left ventricular end-diastolic pressure was 23 +/- 2 mmHg in MI
compared with 8 +/- 2 mmHg in sham-operated controls (Sham, P < 0.001).
Cell shortening was measured in voltage-clamped myocytes at 36 degrees
C. In solutions where Cs$^+$ had been replaced by K$^+$, the
voltage dependence of contraction was sigmoidal between -20 and +100
mV in Sham and MI cells. Verapamil (20 microM) blocked L-type Ca$^2+$
current and reduced contraction in Sham cells by approximately 50\%
(P < 0.01) but did not decrease contraction significantly in MI
cells at test potentials above +10 mV. Verapamil-insensitive contractions
were blocked by Ni$^2+$ (5 mM). Na$^+$/Ca$^2+$ exchange
current was doubled in MI compared with Sham cells at test potentials
between -20 and +80 mV (P < 0.05), whereas mRNA and protein expression
increased by 30-40\%. Finally, voltage dependence of contraction
was bell shaped in Na$^+$-free solutions, but contraction was
significantly increased in MI cells over a wider voltage range
(P < 0.05). The insensitivity to Ca$^2+$ channel block in MI
cells may result from an increased contribution of the Na$^+$/Ca$^2+$
exchanger to triggering of E-C coupling. These results suggest significant
changes in E-C coupling in the hypertrophy and failure that develop
in response to extensive MI.
%0 Journal Article
%1 Wass_2000_H798
%A Wasserstrom, J. A.
%A Holt, E.
%A Sjaastad, I.
%A Lunde, P. K.
%A Odegaard, A.
%A Sejersted, O. M.
%D 2000
%J Am. J. Physiol. Heart Circ. Physiol.
%K 10924080 Animals, Cells, Cesium, Congestive, Contraction, Cultured, Exchanger, Failure, Function, Gov't, Heart Heart, Infarction, Left, Male, Membrane Myocardial Myocardium, Nickel, Non-U.S. P.H.S., Potassium, Potentials, Rats, Research Sodium-Calcium Support, U.S. Ventricles, Ventricular Verapamil, Wistar,
%N 2
%P H798-807
%T Altered E-C coupling in rat ventricular myocytes from failing hearts
6 wk after MI.
%U http://ajpheart.physiology.org/cgi/content/full/279/2/H798
%V 279
%X Excitation-contraction (E-C) coupling was investigated in rat hearts
6 wk after induction of myocardial infarction (MI) by ligation
of the left coronary artery. Heart weight was increased by 74\% and
left ventricular end-diastolic pressure was 23 +/- 2 mmHg in MI
compared with 8 +/- 2 mmHg in sham-operated controls (Sham, P < 0.001).
Cell shortening was measured in voltage-clamped myocytes at 36 degrees
C. In solutions where Cs$^+$ had been replaced by K$^+$, the
voltage dependence of contraction was sigmoidal between -20 and +100
mV in Sham and MI cells. Verapamil (20 microM) blocked L-type Ca$^2+$
current and reduced contraction in Sham cells by approximately 50\%
(P < 0.01) but did not decrease contraction significantly in MI
cells at test potentials above +10 mV. Verapamil-insensitive contractions
were blocked by Ni$^2+$ (5 mM). Na$^+$/Ca$^2+$ exchange
current was doubled in MI compared with Sham cells at test potentials
between -20 and +80 mV (P < 0.05), whereas mRNA and protein expression
increased by 30-40\%. Finally, voltage dependence of contraction
was bell shaped in Na$^+$-free solutions, but contraction was
significantly increased in MI cells over a wider voltage range
(P < 0.05). The insensitivity to Ca$^2+$ channel block in MI
cells may result from an increased contribution of the Na$^+$/Ca$^2+$
exchanger to triggering of E-C coupling. These results suggest significant
changes in E-C coupling in the hypertrophy and failure that develop
in response to extensive MI.
@article{Wass_2000_H798,
abstract = {Excitation-contraction (E-C) coupling was investigated in rat hearts
6 wk after induction of myocardial infarction ({MI}) by ligation
of the left coronary artery. Heart weight was increased by 74\% and
left ventricular end-diastolic pressure was 23 +/- 2 mmHg in {MI}
compared with 8 +/- 2 mmHg in sham-operated controls (Sham, P < 0.001).
Cell shortening was measured in voltage-clamped myocytes at 36 degrees
C. In solutions where {C}s$^+$ had been replaced by {K}$^{+}$, the
voltage dependence of contraction was sigmoidal between -20 and +100
mV in Sham and {MI} cells. Verapamil (20 microM) blocked L-type {C}a$^{2+}$
current and reduced contraction in Sham cells by approximately 50\%
(P < 0.01) but did not decrease contraction significantly in {MI}
cells at test potentials above +10 mV. Verapamil-insensitive contractions
were blocked by {N}i$^{2+}$ (5 mM). {N}a$^{+}$/{C}a$^{2+}$ exchange
current was doubled in {MI} compared with Sham cells at test potentials
between -20 and +80 mV (P < 0.05), whereas m{RNA} and protein expression
increased by 30-40\%. Finally, voltage dependence of contraction
was bell shaped in {N}a$^{+}$-free solutions, but contraction was
significantly increased in {MI} cells over a wider voltage range
(P < 0.05). The insensitivity to {C}a$^{2+}$ channel block in {MI}
cells may result from an increased contribution of the {N}a$^{+}$/{C}a$^{2+}$
exchanger to triggering of E-C coupling. These results suggest significant
changes in E-C coupling in the hypertrophy and failure that develop
in response to extensive {MI}.},
added-at = {2009-06-03T11:20:58.000+0200},
author = {Wasserstrom, J. A. and Holt, E. and Sjaastad, I. and Lunde, P. K. and Odegaard, A. and Sejersted, O. M.},
biburl = {https://www.bibsonomy.org/bibtex/2a4fa01b58e86e30d6f769cc0b8ff8c71/hake},
description = {The whole bibliography file I use.},
file = {Wass_2000_H798.pdf:Wass_2000_H798.pdf:PDF},
interhash = {d8e78525b973100b66cf92df8699f1f0},
intrahash = {a4fa01b58e86e30d6f769cc0b8ff8c71},
journal = {Am. J. Physiol. Heart Circ. Physiol.},
key = 26,
keywords = {10924080 Animals, Cells, Cesium, Congestive, Contraction, Cultured, Exchanger, Failure, Function, Gov't, Heart Heart, Infarction, Left, Male, Membrane Myocardial Myocardium, Nickel, Non-U.S. P.H.S., Potassium, Potentials, Rats, Research Sodium-Calcium Support, U.S. Ventricles, Ventricular Verapamil, Wistar,},
month = Aug,
number = 2,
pages = {H798-807},
timestamp = {2009-06-03T11:21:36.000+0200},
title = {Altered E-C coupling in rat ventricular myocytes from failing hearts
6 wk after {MI}.},
url = {http://ajpheart.physiology.org/cgi/content/full/279/2/H798},
volume = 279,
year = 2000
}