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Differences in the effect of metabolic inhibition on action potentials and calcium currents in endocardial and epicardial cells.

Abstract：

BACKGROUND:Ischemia-induced electrophysiological changes are more prominent in epicardial cells than in endocardial cells. Epicardial action potentials shorten more than endocardial action potentials during ischemia. Since the L-type Ca2+ current plays an important role in the maintenance of action potential duration, we hypothesized that the Ca2+ current is affected more in epicardial cells than in endocardial cells during ischemia. METHODS AND RESULTS:To test this hypothesis, we examined the effect of metabolic inhibition, a major component of ischemia, on action potentials and the Ca2+ current in single cells isolated from the endocardial and epicardial layers of the feline left ventricle. The membrane voltage and current were measured by using the whole-cell mode of the patch-clamp technique. During control periods, action potentials recorded from epicardial myocytes had lower amplitude, a prominent notch between phases 1 and 2, and shorter action potential duration compared with those recorded from endocardial myocytes. However, the amplitude and current-voltage relation of the Ca2+ current were similar in endocardial and epicardial cells at test potentials of -30 to 60 mV elicited from a holding potential of -40 mV. The time course of inactivation of the Ca2+ current also was identical in the two cell types. After 15 minutes of superfusion with glucose-free Tyrode's solution containing 1 mM CN-, action potential duration was reduced by 13 +/- 7% in endocardial cells and by 80 +/- 9% in epicardial cells (p less than 0.01). The peak Ca2+ current was reduced by 21 +/- 9% in endocardial cells and by 37 +/- 6% in epicardial cells (p less than 0.01). CONCLUSIONS:We conclude that enhanced depression of the Ca2+ current may account in part for the greater action potential shortening in epicardial cells during ischemia and metabolic inhibition.

journal_name

Circulation

journal_title

Circulation

authors

Kimura S,Bassett AL,Furukawa T,Furukawa N,Myerburg RJ

doi

10.1161/01.cir.84.2.768

subject

Has Abstract

pub_date

1991-08-01 00:00:00

pages

768-77

issue

eissn

0009-7322

issn

1524-4539

journal_volume

pub_type

杂志文章

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Differences in the effect of metabolic inhibition on action potentials and calcium currents in endocardial and epicardial cells.