Single L-type Ca(2+) channel regulation by cGMP-dependent protein kinase type I in adult cardiomyocytes from PKG I transgenic mice.
OBJECTIVE
Calcium entry via the L-type Ca(2+) channel (LTCC) is crucial for excitation-contraction (EC) coupling and activation of Ca(2+)-dependent signal transduction pathways in cardiac myocytes. Both nitric oxide (NO), signaling via cGMP, and acetylcholine, signaling via the muscarinic receptor, have been identified as negative regulators of beta-adrenoreceptor-stimulated LTCC activity in cardiac myocytes.


METHODS
To examine the potential role of cGMP-dependent protein kinase type I (PKG I) in the inhibitory effects of NO/cGMP and the muscarinic receptor on LTCC activity, we generated transgenic (TG) mice overexpressing PKG I selectively in cardiac myocytes under the control of the alpha-myocin heavy chain promoter. Single LTCC-gating properties were assessed in isolated ventricular myocytes from adult wild-type (WT) and PKG I transgenic (TG) mice.


RESULTS
Basal LTCC activity (peak average current, mean open probability, mean availability) was significantly decreased by the nitric oxide donor DEA-NO (0.1 micromol/l) and the cGMP-analog 8-Br-cGMP (1 mmol/l) in TG but not in WT cardiac myocytes. Conversely, muscarinic (carbachol, 1 micromol/l) stimulation had no significant effect on basal LTCC activity in either WT or TG cardiac myocytes. beta-Adrenergic stimulation with isoproterenol (1 micromol/l) increases single LTCC activity in WT and TG cardiac myocytes to the same extent. The inhibitory effects of DEA-NO and 8-Br-cGMP on isoproterenol activation of the LTCC current were significantly enhanced in TG as compared to WT cardiac myocytes. By contrast, carbachol inhibition of isoproterenol-stimulated single LTCC activity was not enhanced in TG cardiac myocytes.


CONCLUSIONS
Transgenic overexpression of PKG I augments NO/cGMP inhibition but not muscarinic inhibition of single LTCC activity, indicating that PKG I is a downstream target for NO/cGMP, but not the muscarinic receptor in adult cardiac myocytes.
Schröder
Frank
F
Department of Cardiology and Angiology, Hannover Medical School, Carl-Neuberg-Str 1, 30625 Hannover, Germany. schroder.f@mh-hannover.de
Klein
Gunnar
G
Fiedler
Beate
B
Bastein
Michaela
M
Schnasse
Nicole
N
Hillmer
Anja
A
Ames
Sandra
S
Gambaryan
Stepan
S
Drexler
Helmut
H
Walter
Ulrich
U
Lohmann
Suzanne M
SM
Wollert
Kai C
KC
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D006834:Hydrazines / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides
D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents; D006834:Hydrazines; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009569:Nitric Oxide; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D002217:Carbachol; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D007545:Isoproterenol