Biochemical and Biophysical Research Communications 2007-08-03

An outwardly rectifying anionic background current in atrial myocytes from the human heart.

H Li, H Zhang, J C Hancox, R Z Kozlowski

Index: Biochem. Biophys. Res. Commun. 359 , 765-70, (2007)

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Abstract

This report describes a hitherto unreported anionic background current from human atrial cardiomyocytes. Under whole-cell patch-clamp with anion-selective conditions, an outwardly rectifying anion current (I(ANION)) was observed, which was larger with iodide than nitrate, and with nitrate than chloride as charge carrier. In contrast with a previously identified background anionic current from small mammal cardiomyocytes, I(ANION) was not augmented by the pyrethroid tefluthrin (10 microM); neither was it inhibited by hyperosmolar external solution nor by DIDS (200 microM); thus I(ANION) was not due to basal activity of volume-sensitive anion channels. I(ANION) was partially inhibited by the Cl(-) channel blockers NPPB (50 microM) and Gly H-101 (30 microM). Incorporation of I(ANION) into a human atrial action potential (AP) simulation led to depression of the AP plateau, accompanied by alterations to plateau inward calcium current, and to AP shortening at 50% but not 90% of complete repolarization, demonstrating that I(ANION) can influence the human atrial AP profile.