Developmental expression of a functional TASK-1 2P domain K<sup>+ </sup>channel in embryonic chick heart
<p>Abstract</p> <p>Background</p> <p>Background K<sup>+ </sup>channels are the principal determinants of the resting membrane potential (RMP) in cardiac myocytes and thus, influence the magnitude and time course of the action potential (AP).</p> <p&...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
BMC
2009-11-01
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| Series: | Journal of Biomedical Science |
| Online Access: | http://www.jbiomedsci.com/content/16/1/104 |
| Summary: | <p>Abstract</p> <p>Background</p> <p>Background K<sup>+ </sup>channels are the principal determinants of the resting membrane potential (RMP) in cardiac myocytes and thus, influence the magnitude and time course of the action potential (AP).</p> <p>Methods</p> <p>RT-PCR and <it>in situ </it>hybridization are used to study the distribution of TASK-1 and whole-cell patch clamp technique is employed to determine the functional expression of TASK-1 in embryonic chick heart.</p> <p>Results</p> <p>Chicken TASK-1 was expressed in the early tubular heart, then substantially decreased in the ventricles by embryonic day 5 (ED5), but remained relatively high in ED5 and ED11 atria. Unlike TASK-1, TASK-3 was uniformly expressed in heart at all developmental stages. <it>In situ </it>hybridization studies further revealed that TASK-1 was expressed throughout myocardium at Hamilton-Hamburger stages 11 and 18 (S11 & S18) heart. In ED11 heart, TASK-1 expression was more restricted to atria. Consistent with TASK-1 expression data, patch clamp studies indicated that there was little TASK-1 current, as measured by the difference currents between pH 8.4 and pH 7.4, in ED5 and ED11 ventricular myocytes. However, TASK-1 current was present in the early embryonic heart and ED11 atrial myocytes. TASK-1 currents were also identified as 3 μM anandamide-sensitive currents. 3 μM anandamide reduced TASK-1 currents by about 58% in ED11 atrial myocytes. Zn<sup>2+ </sup>(100 μM) which selectively inhibits TASK-3 channel at this concentration had no effect on TASK currents. In ED11 ventricle where TASK-1 expression was down-regulated, I<sub>K1 </sub>was about 5 times greater than in ED11 atrial myocytes.</p> <p>Conclusion</p> <p>Functional TASK-1 channels are differentially expressed in the developing chick heart and TASK-1 channels contribute to background K<sup>+ </sup>conductance in the early tubular embryonic heart and in atria. TASK-1 channels act as a contributor to background K<sup>+ </sup>current to modulate the cardiac excitability in the embryonic heart that expresses little I<sub>K1</sub>.</p> |
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| ISSN: | 1021-7770 1423-0127 |