AJP - Heart and Circulatory Physiology, Vol 256, Issue 5 1505-H1508, Copyright © 1989 by American Physiological Society

ARTICLES

Low-threshold current is major calcium current in chick ventricle cells

S. Kawano and R. L. DeHaan
Department of Anatomy and Cell Biology, Emory University Health Sciences Center, Atlanta, Georgia 30322.

Single myocytes were dissociated from the apical ventricles of 14-day-old chick embryos and were maintained in culture for 24 h. Isolated rounded cells, 13-18 microns in diameter with input capacitance averaging 5.2 pF, were selected for whole cell patch-clamp analysis of calcium current (ICa). Two current components, T-type (IT) and L-type (IL), were identified by differences in their voltage thresholds and pharmacological sensitivity, IL was activated by depolarizing steps from -40 mV and was selectively blocked by 1 microM D 600 (methoxyverapamil). IT was obtained by subtracting IL from total ICa and was blocked by 120 microM Ni2+. Identified by threshold potential, sensitivity to Ni2+, or resistance to D 600, IT had a greater current density than has been reported in any adult cardiac tissue. It was also larger than IL and was therefore the major contributor to ICa in this preparation.

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