2,4-dinitrophenol acutely inhibits rabbit atrial Ca2+-sensitive Cl- current (I-TO2)

We investigated the effects of 2,4-dinitrophenol (DNP), the uncoupler of mi tochondrial oxidative phosphorylation, on the Ca2+-sensitive Cl- current co mponent of the transient outward current (I-TO2). Amphotericin B perforated -patch, whole-cell patch-clamp technique was employed (35 degrees C) using enzymatically isolated single rabbit atrial myocytes. We defined I-TO2 as t he amplitude of the 2 mM 4-aminopyridine resistant transient outward curren t sensitive to anthracene-9-carboxylic acid (A9C). Between +5 and +45 mV, 0 .2 mM A9C inhibited I-TO2 by similar to 70% (n = 13). Within 30 s after app lication of 0.2 mM DNP, both normal I-TO2 transients (n = 8) and the I-TO2 transients that remained after A9C treatment (n = 8) were inhibited complet ely. In cells expressing I-TO2 (70% of total), DNP also suppressed an A9C-i nsensitive slow outward current by similar to 40%, but the holding current at -80 mV was unaffected. There was a similar to 2 min latency between inhi bitory effects of DNP and subsequent membrane current increase, presumably caused by activation of the ATP-sensitive K+ channels (n = 16). We conclude that DNP acutely inhibits I-TO2 via a mechanism presumably separate from m etabolic inhibition.