Calcium Current Measurements in Acutely Isolated Neonatal Cardiac Myocytes

Abstract

ABSTRACT: Action potentials and voltage clamp-induced ionic currents were recorded in acutely isolated neonatal rabbit cardiac myocytes using the whole-cell voltage clamp technique. Time- and voltage-dependent Ca²⁺ currents in neonatal myocytes were elicited by depolarizations from a holding potential of —80 mV to various clamp potentials. The maximal measured inward Ca²⁺ current was 206 ± 10 pA (mean ± SEM, n = 51). The peak current occurred at a mean membrane potential of 7.8 ± 1.3 mV (n = 51). The Ca²⁺ current voltage relation was shifted 26 mV in the positive direction when the external Ca²⁺ concentration was increased 10-fold. Ca²⁺ current rundown was observed with a half-time of approximately 20 min. Cells dialyzed with solution containing the Ca²⁺ chelating agent, EGTA (0.04 mM), had action potential durations similar to those previously reported in papillary muscle. In contrast, a higher concentration of EGTA (14 mM) prolonged the action potential duration. Control of the cell internal ionic composition was achieved by dialysis of the cell with a time constant for Na⁺ ions of 1.2 to 2.6 min. Tetrodotoxin (10 μM), included in some experiments to block Ca²⁺ entry via Na⁺ channels, was shown to be more than 98% effective. These results characterize the whole-cell voltage clamp technique as applied to immature heart cells.

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD