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Different intracellular polyamine concentrations underlie the difference in the inward rectifier K(+) currents in atria and ventricles of the guinea-pig heart.
J Physiol. 2005 Mar 15; 563(Pt 3):713-24.JP

Abstract

The outward component of the strong inward rectifier potassium current, I(K1), is significantly larger in ventricles than in atria of the heart, resulting in faster repolarization at the final phase of the action potential in ventricles. However, the underlying mechanism of the difference in I(K1) remains poorly understood. I(K1) channels are composed of subunits from the Kir2 subfamily, and I(K1) amplitude is determined by the voltage-dependent blockade of the channel by the intracellular polyamines spermine and spermidine, and by Mg(2+). Using a perforated patch-clamp method, which minimizes changes in the intracellular polyamine and Mg(2+) concentrations, we detected repolarization-induced outward I(K1) transients, which are caused by competition between Mg(2+) and spermine to block the channel, in ventricular but not in atrial myocytes from guinea-pig heart. The contribution of the Kir2.3 subunit to the I(K1) channel was found to be minor in the guinea-pig heart, because the activation time course of the Kir2.3 currents was approximately 10-fold slower than those of I(K1), and the marked external pH sensitivity of the Kir2.3 currents was not found in I(K1). Both the Kir2.1 and Kir2.2 currents recorded from inside-out patches exhibited outward transients similar to those of ventricular I(K1) in the presence of 5-10 microM spermine and 0.6-1.1 mM Mg(2+), and their amplitudes were diminished by increasing the spermine or spermidine concentrations. The total and free polyamine concentrations in guinea-pig cardiac tissues were higher in atria than ventricles. These results strongly suggest that different intracellular polyamine concentrations are responsible for the difference in atrial and ventricular I(K1) of the guinea-pig heart.

Authors+Show Affiliations

Department of Physiology, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan. keiko@med.saga-u.ac.jp.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15668212

Citation

Yan, Ding-Hong, et al. "Different Intracellular Polyamine Concentrations Underlie the Difference in the Inward Rectifier K(+) Currents in Atria and Ventricles of the Guinea-pig Heart." The Journal of Physiology, vol. 563, no. Pt 3, 2005, pp. 713-24.
Yan DH, Nishimura K, Yoshida K, et al. Different intracellular polyamine concentrations underlie the difference in the inward rectifier K(+) currents in atria and ventricles of the guinea-pig heart. J Physiol. 2005;563(Pt 3):713-24.
Yan, D. H., Nishimura, K., Yoshida, K., Nakahira, K., Ehara, T., Igarashi, K., & Ishihara, K. (2005). Different intracellular polyamine concentrations underlie the difference in the inward rectifier K(+) currents in atria and ventricles of the guinea-pig heart. The Journal of Physiology, 563(Pt 3), 713-24.
Yan DH, et al. Different Intracellular Polyamine Concentrations Underlie the Difference in the Inward Rectifier K(+) Currents in Atria and Ventricles of the Guinea-pig Heart. J Physiol. 2005 Mar 15;563(Pt 3):713-24. PubMed PMID: 15668212.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Different intracellular polyamine concentrations underlie the difference in the inward rectifier K(+) currents in atria and ventricles of the guinea-pig heart. AU - Yan,Ding-Hong, AU - Nishimura,Kazuhiro, AU - Yoshida,Kaori, AU - Nakahira,Kei, AU - Ehara,Tsuguhisa, AU - Igarashi,Kazuei, AU - Ishihara,Keiko, Y1 - 2005/01/24/ PY - 2005/1/26/pubmed PY - 2005/6/25/medline PY - 2005/1/26/entrez SP - 713 EP - 24 JF - The Journal of physiology JO - J Physiol VL - 563 IS - Pt 3 N2 - The outward component of the strong inward rectifier potassium current, I(K1), is significantly larger in ventricles than in atria of the heart, resulting in faster repolarization at the final phase of the action potential in ventricles. However, the underlying mechanism of the difference in I(K1) remains poorly understood. I(K1) channels are composed of subunits from the Kir2 subfamily, and I(K1) amplitude is determined by the voltage-dependent blockade of the channel by the intracellular polyamines spermine and spermidine, and by Mg(2+). Using a perforated patch-clamp method, which minimizes changes in the intracellular polyamine and Mg(2+) concentrations, we detected repolarization-induced outward I(K1) transients, which are caused by competition between Mg(2+) and spermine to block the channel, in ventricular but not in atrial myocytes from guinea-pig heart. The contribution of the Kir2.3 subunit to the I(K1) channel was found to be minor in the guinea-pig heart, because the activation time course of the Kir2.3 currents was approximately 10-fold slower than those of I(K1), and the marked external pH sensitivity of the Kir2.3 currents was not found in I(K1). Both the Kir2.1 and Kir2.2 currents recorded from inside-out patches exhibited outward transients similar to those of ventricular I(K1) in the presence of 5-10 microM spermine and 0.6-1.1 mM Mg(2+), and their amplitudes were diminished by increasing the spermine or spermidine concentrations. The total and free polyamine concentrations in guinea-pig cardiac tissues were higher in atria than ventricles. These results strongly suggest that different intracellular polyamine concentrations are responsible for the difference in atrial and ventricular I(K1) of the guinea-pig heart. SN - 0022-3751 UR - https://www.unboundmedicine.com/medline/citation/15668212/Different_intracellular_polyamine_concentrations_underlie_the_difference_in_the_inward_rectifier_K_+__currents_in_atria_and_ventricles_of_the_guinea_pig_heart_ L2 - https://doi.org/10.1113/jphysiol.2004.077677 DB - PRIME DP - Unbound Medicine ER -