Functional and transmural modulation of M cell behavior in canine ventricular wall

Norihiro Ueda, Douglas P. Zipes, Jiashin Wu

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Previous studies have demonstrated a discrete population of midmyocardial (M) cells in the ventricular myocardium having excessive action potential duration (APD) prolongation during long activation cycle lengths (CL) and under the influence of APD-prolonging agents. However, M cells have not been found in other studies. Existing explanations for the discrepancies appear inadequate. We hypothesized that instead of being a discrete group, M cell behavior is functional and conditionally expressed. We mapped APDs on the cut-exposed transmural surfaces of arterially perfused ventricular wedges from 26 dogs during Na+ current modification with anemone toxin II (ATX-II). Compared with the endocardium, APDs were not statistically different in the parallel layer having the longest mean APD (APDL) and were significantly shorter in the epicardium in the 26 wedges before ATX-II. ATX-II (>5 nmol/l) prolonged APD heterogeneously (midmyocardium > endocardium > epicardium). The differences increased at longer CLs. ATX-II (20.0 nmol/l) shifted the APDL layer to 32 ± 6.2% (6 wedges, CL: 4,000 ms) of the transmural thickness from the (sub)endocardium (8.6 ± 7.2%, 26 wedges, ATX-II free). We detected the presence of M cell behavior (significantly longer APDs in the APDL layer than in the endocardium and epicardium, P ≤ 0.04, CL: 4,000 ms) in the 18 wedges having ≥ 5 nmol/l ATX-II but not (P > 0.36) in the other 18 wedges having ≤ 2.5 nmol/l ATX-II. Both the position of the APDL layer and presence of M cell-like behavior were modulated by ATX-II. The dynamic spatial modulation indicates that M cell behavior is functional and only becomes manifest under suitable conditions.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume287
Issue number6 56-6
DOIs
StatePublished - Dec 2004

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Anemone
pamidronate
Canidae
Endocardium
Action Potentials
Pericardium
Myocardium
Dogs

Keywords

  • Long QT syndrome
  • Optical mapping
  • Repolarization dispersion

ASJC Scopus subject areas

  • Physiology

Cite this

Functional and transmural modulation of M cell behavior in canine ventricular wall. / Ueda, Norihiro; Zipes, Douglas P.; Wu, Jiashin.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 287, No. 6 56-6, 12.2004.

Research output: Contribution to journalArticle

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