Potentiation of slow component of delayed rectifier K+ current by cGMP via two distinct mechanisms: inhibition of phosphodiesterase 3 and activation of protein kinase G

• Published in: British journal of pharmacology Vol. 137; no. 1; pp. 127 - 137
• Main Authors: SHIMIZU, Kentaro, SHINTANI, Yutaka, DING, Wei-Guang, MATSUURA, Hiroshi, BAMBA, Tadao
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 01.09.2002
• Subjects: 1-Methyl-3-isobutylxanthine - pharmacology; 3',5'-Cyclic-AMP Phosphodiesterases - metabolism; Animals; Atrial Natriuretic Factor - pharmacology; Atrial Natriuretic Factor - physiology; Biological and medical sciences; Cyclic GMP - analogs & derivatives; Cyclic GMP - physiology; Cyclic GMP-Dependent Protein Kinases - metabolism; Cyclic Nucleotide Phosphodiesterases, Type 3; Delayed Rectifier Potassium Channels; Enzyme Activation; Female; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Heart; In Vitro Techniques; Membrane Potentials; Patch-Clamp Techniques; Phosphodiesterase Inhibitors - pharmacology; Potassium Channels - physiology; Potassium Channels, Voltage-Gated; Sinoatrial Node - cytology; Sinoatrial Node - metabolism; Vertebrates: cardiovascular system; Heart; Sinus node; Electrophysiology; cGMP; Esterases; Ionic channel; Phosphoric diester hydrolases; guinea-pig; Guinea pig; cyclic GMP-inhibited phosphodiesterase; protein kinase G; sino-atrial node cells; atrial natriuretic peptide; milrinone; 8-bromo-cyclic GMP; 3',5'-Cyclic-nucleotide phosphodiesterase; Enzyme; Transferases; Rodentia; Enzyme inhibitor; 3',5'-GMP; In vitro; Biological activity; Vertebrata; Mammalia; Protein kinase; Animal; Myocardium; Slowly activating component of delayed rectifier K+ current; Hydrolases; Circulatory system; Potassium
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704843

1. Regulation of the slowly activating component of delayed rectifier K(+) current (I(Ks)) by intracellular guanosine 3'5' cyclic monophosphate (cGMP) was investigated in guinea-pig sino-atrial (SA) node cells using the whole-cell patch-clamp method. 2. When a cell was dialyzed with pipette solution containing 100 micro M cGMP, I(Ks) started to gradually increase and reached a maximum increase of a factor of 2.37 +/- 0.39 (n = 4) about 10-15 min after rupture of patch membrane. Atrial natriuretic peptide (ANP, 100 nM) also potentiated I(Ks), consistent with intracellular cGMP-induced enhancement of I(Ks). 3. Bath application of a selective blocker of the cGMP-inhibited phosphodiesterase (PDE3) milrinone (100 microM) enhanced I(Ks) by a factor of 1.50 +/- 0.09 (n = 4) but failed to further enhance I(Ks) after a maximum stimulation by intracellular cGMP (100 microM), suggesting that blockade of PDE3 activity is involved in the enhancement of I(Ks). A potent but nonspecific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX, 100 microM) further increased I(Ks) stimulated by 100 microM milrinone, indicating that PDE subtypes other than PDE3 are also involved in the regulation of basal I(Ks) in guinea-pig SA node cells. 4. Bath application of 100 microM 8-bromoguanosine 3'5' cyclic monophosphate (8-Br-cGMP) increased I(Ks) by a factor of 1.48 +/- 0.11 (n = 5) and this stimulatory effect was totally abolished by cGMP-dependent protein kinase (PKG) inhibitor KT-5823 (500 nM), suggesting that the activation of PKG also mediates cGMP-induced potentiation of I(Ks). 5. These results strongly suggest that intracellular cGMP potentiates I(Ks) not only by blocking PDE3 but also by activating PKG in guinea-pig SA node cells.