Use of the cell-attached patch clamp technique to examine regulation of single cardiac K channels by cyclic GMP
✍ Scribed by Gordon M. Wahler; Nicholas Sperelakis
- Publisher
- Springer
- Year
- 1989
- Tongue
- English
- Weight
- 513 KB
- Volume
- 80
- Category
- Article
- ISSN
- 0300-8177
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✦ Synopsis
Cyclic nucleotides play a central role in the modulation of ion channels in a variety of tissues, including the heart. In order to determine the possible role of cyclic GMP (cGMP) in the regulation of the background K channel activity of cardiac cells, the effect of 8-Br-cGMP on the inwardly-rectifying K channels of cultured ventricular myocytes from embryonic chick hearts was examined. 8-Br-cGMP (10(-4) to 10(-3) M) inhibited these single channel currents within 3 to 10 min. Spontaneous recovery of the currents occurred with prolonged (greater than or equal to 15 min) exposure to 8-Br-cGMP, but this recovery was accompanied by altered channel behavior. Thus, a new long-lasting open state of the channel appeared, in addition to the open state observed prior to 8-Br-cGMP addition. Superfusion of the cells with the muscarinic agonist carbamylcholine (10(-5) M) also resulted in inhibition of the currents, which suggests that the cGMP-mediated inhibition of these channels may occur under physiological conditions. Thus, it appears that cGMP may be an important modulator of the background K conductance (and excitability) of cardiac cells.