Transient outward and delayed rectifier currents in canine atrium: properties and role of isolation methods

Abstract

Although the dog is the principal species used for in vivo studies of atrial arrhythmias, little is known about currents governing canine atrial repolarization. Cells were isolated from dog atria by exposure to collagenase of tissue in vitro ("chunk cells") and by arterial perfusion ("perfusion cells"). Whole cell voltage clamp revealed transient outward K+ current (Ito1), Ca(2+)-dependent Cl- current (Ito2), and delayed rectifier K+ current (IK). Ito1 recovered rapidly and showed little frequency dependence. Two components of IK were present as follows: a rapidly activating E-4031-sensitive current with marked inward recitification and a slower-activating E-4031-insensitive component. Ito1 and IK resembled corresponding currents previously described in human atrium. Transient outward currents were similar in chunk and perfusion cells, but IK was seen in 4% of chunk cells vs. 99% of perfusion cells (P < 0.001). Suppression of each identified current retarded canine action potential repolarization. We conclude that Ito1, Ito2, and both components of IK are present in dog atrium, IK is much more sensitive to the isolation method than Ito1 or Ito2, and the properties of two important repolarizing currents (Ito1 and IK) previously described in human atrium are similar to those in dog atrium.

Permeability characteristics of monovalent cations in atrial myocytes of the rat heart

“…We have also failed to identify IKr in rat atrial myocytes under normal ionic conditions, but could detect it in isotonic Cs¤ solution. To our knowledge, the presence of IKr in rat atrial myocytes is shown for the first time in the present study, although it has been reported previously in canine (Yue et al 1996), human (Wang et al 1994) and guinea-pig atrial myocytes (Horie et al 1990;Sanguinetti & Jurkiewicz, 1991 A, effect of E-4031 (5 ìÒ) on membrane currents. Nicardipine (1 ìÒ) was included in the bath solution.…”

Hyperglycemia aggravates atrial interstitial fibrosis, ionic remodeling and vulnerability to atrial fibrillation in diabetic rabbits

“…Micrographs were digitized using Photoshop 7.0 (Adobe, San Jose, CA), and areas of fibrosis were analyzed using Image Pro Plus 4.5 Scion image software (Scion Co., Frederick, MD). Whole-cell patch-clamp studies In our study, experimental procedures were complied with previously developed methods (13)(14)(15). Another twenty rabbits were used for whole-cell patch-clamp studies.…”

Effects of Experimental Heart Failure on Atrial Cellular and Ionic Electrophysiology

“…Hearts were excised and atrial cells isolated from RA pectinate muscles as previously described. 10 In vivo studies were performed in the first 8 control and 18 CHF dogs. Because performing both in vivo and in vitro studies in each dog greatly prolonged the experiments, subsequent dogs were used for in vitro study only, after it had been verified that in vitro results were similar whether or not they were preceded by in vivo study.…”

“…I K is very sensitive to isolation procedures, 10 and therefore, changes in isolation technique could contribute to differences in I K when several groups are compared. To minimize possible effects of time-dependent changes in enzymes, isolation procedure, etc, animals from each group were studied concurrently in an alternating fashion.…”