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Action potential duration and endocardial modulation of myocardial contraction in the ferret
A M Shah1, M J Shattock, M J Lewis
1University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom.
Objective:
Endocardial endothelium releases substances which modulate myocardial contraction. Selective endocardial removal abbreviates contraction by removing a contraction prolonging substance "endocardin". The aim of the study was to investigate whether changes in action potential duration underlie these contractile effects.
Methods:
The contractile effects of shortening the action potential were first characterised, using a potassium channel "opener" cromakalim (3 microM). Transmembrane action potentials were then recorded in isolated ferret papillary muscles before and after endocardial removal.
Results:
Cromakalim-induced action potential abbreviation reduced contractile twitch duration. Endocardial removal itself however did not alter action potential duration.
Conclusions:
Endocardial modulation of cardiac contraction does not involve changes in action potential duration.