Na+-Ca2+ exchange transport and pacemaker activity of the rabbit SA node.
10.3349/ymj.1991.32.3.223
- Author:
So Ra PARK
1
;
Chang Kook SUH
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:
Rabbit;
SA node;
pacemaker activity;
Na+-Ca2+ exchange;
Na+-selective electrode;
Intracelluar Na+ activity
- MeSH:
Action Potentials;
Animal;
Biological Transport;
Calcium/*metabolism/physiology;
Electrophysiology;
Female;
Male;
Pacemaker, Artificial;
Rabbits;
Sinoatrial Node/*metabolism/physiology;
Sodium/*metabolism/physiology;
Support, Non-U.S. Gov't
- From:Yonsei Medical Journal
1991;32(3):223-230
- CountryRepublic of Korea
- Language:English
-
Abstract:
Recent electrophysiological data have provided the evidences that background currents such as Na(+)-Ca2+ exchange can significantly modulate cardiac pacemaker activity. In this study, the effects of extracellular Na+ and Ca2+ concentrations on the pacemaker activity were investigated by measuring the intracellular Na+ activity (aiNa) with Na(+)-selective microelectrodes and the results are summarized as follows. 1) In the rabbit SA node, aiNa was 3.2 +/- 0.3 mM and mean MDP (maximal diastolic potential) was -63.3 +/- 1.4 mV. 2) Graded decreases of external Na+ concentration resulted in the loss of spontaneous beating, hyperpolarization and the decrease of aiNa. 3) An increase in extracellular Ca2+ concentration in low Na+ solution augmented the transient decrease of aiNa, about 3 minutes in low Na+ solution, until aiNa started to increase. 4) In low Na+ solution, which had extracellular Ca2+ concentration according to the calculation based on the equilibrium state of Na+-Ca2+ exchange, aiNa was continuously decreased. It was concluded that intracellular Na+ activity modulated by Na+-Ca2+ exchange could play an important role in the initiation of pacemaker potential.
