Mechanism of Low K+-induced Depolarization in Mammalian Cardiac Muscle.
10.3349/ymj.1987.28.3.176
- Author:
Duck Sun AHN
1
;
Syng Ill LEE
;
Doo Hee KANG
Author Information
1. Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Canine Purkinges fiber;
low external K+;
membrane depolarization
- MeSH:
Animal;
Dogs;
Guinea Pigs;
Heart/physiology*;
Membrane Potentials/drug effects*;
Papillary Muscles/physiology;
Potassium/pharmacology*;
Purkinje Fibers/physiology;
Rest
- From:Yonsei Medical Journal
1987;28(3):176-182
- CountryRepublic of Korea
- Language:English
-
Abstract:
The membrane permeability to potassium at a resting state is greater than to any other ions and the maintenance of resting membrane potential is largely dependent on K+ concentration of outside medium (Hodgkin and Horowicz 1959), i.e. an increase of K+ concentration of medium induces a depolarization, vice versa. However, on the contrary to this prediction, in some mammalian heart muscle a reduction of external K+ concentration induces a depolarization of membrane potential rather than a hyperpolarization (Vassalle 1965). In this study it was aimed to elucidate the possible mechanism of spontaneous depolarization induced by low external K+ in canine Purkinje fibers. The membrane potential was constantly recorded while components of cations in the bathing medium were replaced one by one by equimolar sucrose until the low K+ induced depolarization was blocked. The results are summarized as follows; The membrane potential of canine Purkinje fibers was spontaneously depolarized by low external K+, and the magnitude of depolarization was not affected by verapamil TEA, and a partial replacement of external Na+ and Ca2+ with choline chloride. But the membrane potential was hyperpolarized only when the all external cations were substitued with sucrose; and this hyperpolarization was disappeared again by substitution of sucrose with choline chloride. From these results, it may be concluded that the depolarization induced by low external K+ in canine Purkinje fibers is due to the nonspecific increase of membrane permeability to external cations and/or combinations with decreased K+ conductance.
