Docosahexaenoic acid has influence on action potentials and transient outward potassium currents of ventricular myocytes.
BACKGROUND
There are many reports about the anti-arrhythmic effects of omega-3 polyunsaturated fatty acids, however, the mechanisms are still not completely delineated. The purpose of this study was to investigate the characteristics of action potentials and transient outward potassium currents (Ito) of Sprague-Dawley rat ventricular myocytes and the effects of docosahexaenoic acid (DHA) on action potentials and Ito.


METHODS
The calcium-tolerant rat ventricular myocytes were isolated by enzyme digestion. Action potentials and Ito of epicardial, mid-cardial and endocardial ventricular myocytes were recorded by whole-cell patch clamp technique.


RESULTS
1. Action potential durations (APDs) were prolonged from epicardial to endocardial ventricular myocytes (P < 0.05). 2. Ito current densities were decreased from epicardial to endocardial ventricular myocytes, which were 59.50 +/- 15.99 pA/pF, 29.15 +/- 5.53 pA/pF, and 12.29 +/- 3.62 pA/pF, respectively at +70 mV test potential (P < 0.05). 3. APDs were gradually prolonged with the increase of DHA concentrations from 1 micromol/L to 100 micromol/L, however, APDs changes were not significant as DHA concentrations were in the range of 0 micromol/L to 1 micromol/L. 4. Ito currents were gradually reduced with the increase of DHA concentrations from 1 micromol/L to 100 micromol/L, and its half-inhibited concentration was 5.3 micromol/L. The results showed that there were regional differences in the distribution of action potentials and Ito in rat epicardial, mid-cardial and endocardial ventricular myocytes. APDs were prolonged and Ito current densities were gradually reduced with the increase of DHA concentrations.


CONCLUSIONS
The anti-arrhythmia mechanisms of DHA are complex, however, the effects of DHA on action potentials and Ito may be one of the important causes.
Wang
Ru-xing
RX
Department of Cardiology, Affiliated Hospital of Nanjing Medical University in Wuxi, China. ruxingw@sina.com.cn
Li
Xiao-rong
XR
Guo
Tao
T
Sun
Li-ping
LP
Guo
Su-xia
SX
Yang
Zhen-Yu
ZY
Yang
Xiang-Jun
XJ
Jiang
Wen-ping
WP
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D022062:Electrophysiologic Techniques, Cardiac; D055724:Electrophysiological Phenomena / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000889:Anti-Arrhythmia Agents; D004281:Docosahexaenoic Acids; D011188:Potassium
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