spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online January 19, 2006
Journal of Experimental Biology 209, 549-557 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02044
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Haverinen, J.
Right arrow Articles by Vornanen, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Haverinen, J.
Right arrow Articles by Vornanen, M.

Significance of Na+ current in the excitability of atrial and ventricular myocardium of the fish heart

Jaakko Haverinen and Matti Vornanen*

University of Joensuu, Department of Biology, PO Box 111, 80101 Joensuu, Finland


Figure 1
View larger version (13K):

[in a new window]
  		Fig. 1. Action potentials of the rainbow trout heart. Action potentials were recorded with microelectrodes from intact cardiac tissue at 4°C. (A) Representative recordings of atrial and ventricular action potentials. (B) The rising phase of atrial and ventricular action potentials and their first derivatives, indicating the rate of action potential upstroke.

 

Figure 2
View larger version (21K):

[in a new window]
  		Fig. 2. Comparison of voltage-dependent properties of INa between atrial and ventricular myocytes of the rainbow trout heart. Current-voltage relationships and steady-state activation m{infty} and inactivation curves h{infty} of the INa are shown in A and B, respectively. Voltage protocols (top), representative recordings (middle) and mean results (± s.e.m.; N=12-14) (bottom) are shown. Asterisks show a significant difference (P<0.05) between atrial and ventricular myocytes.

 

Figure 3
View larger version (24K):

[in a new window]
  		Fig. 3. Time-dependent properties of INa in atrial and ventricular myocytes of the rainbow trout heart. (A) Development of rested-state inactivation of INa. Increased duration of the prepulse at -80 mV reduces INa elicited by the test pulse to -20 mV for 30 ms. (B) Recovery of INa from inactivation (reactivation). The amplitude of INa elicited by test pulses to -20 mV for 100 ms increases as a function of the time interval between the prepulse P1 and the test pulse P2. Voltage protocols of INa are shown at the top, representative recordings in the middle and mean (± s.e.m.) results from 9-14 myocytes at the bottom. Asterisks show a significant difference (P<0.05) between atrial and ventricular myocytes.

 

Figure 4
View larger version (21K):

[in a new window]
  		Fig. 4. Voltage dependence of inactivation and activation kinetics of INa in atrial and ventricular myocytes of the rainbow trout heart. (A) Representative tracings of INa at -20 mV. (B) Mean (± s.e.m.) time constant of inactivation ({tau}) and (C) time-to-peak current at different voltages. The results are means (± s.e.m.) of 12-14 myocytes. Asterisks show a significant difference (P<0.05) between atrial and ventricular myocytes.

 

Figure 5
View larger version (15K):

[in a new window]
  		Fig. 5. INa under action potential clamp. Representative atrial and ventricular action potentials (top) were used to elicit tetrodotoxin-sensitive INa (middle) at physiological external Na+ concentration (154 mmol l-1). The bottom panel shows Vmax mean (± s.e.m.; N=12) calculated from INa, Vmax measured in the intact tissue and their difference. Asterisks show a significant difference (P<0.05) between atrial and ventricular myocytes.

 

Figure 6
View larger version (20K):

[in a new window]
  		Fig. 6. Comparison of the voltage threshold for net inward current in isolated atrial and ventricular myocytes of the rainbow trout heart. (A) Currents were elicited from the holding potential of -82 mV muscle by 30 ms depolarising pulses in 2 mV increments. (B) Representative recordings of whole-cell membrane currents (Im) from atrial and ventricular myocytes. The horizontal line indicates the zero membrane potential. (C) Mean (± s.e.m.; N=6-9) current-voltage relations of atrial and ventricular myocytes indicating the threshold for the net inward current. Asterisks show a significant difference (P<0.05) between atrial and ventricular myocytes.

 




© The Company of Biologists Ltd 2006