Premium
Regulation of the L‐type Ca 2+ channel during cardiomyogenesis: switch from NO to adenylyl cyclase‐mediated inhibition
Author(s) -
JI G. J.,
FLEISCHMANN B. K.,
BLOCH W.,
FEELISCH M.,
ANDRESSEN C.,
ADDICKS K.,
HESCHELER J.
Publication year - 1999
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.13.2.313
Subject(s) - adenylyl cyclase , chemistry , adcy6 , microbiology and biotechnology , adcy9 , enzyme , biochemistry , biology
In adult mammalian cardiomyocytes, stimulation of muscarinic receptors counterbalances the β‐adrenoceptor‐mediated increase in myocardial contractility and heart rate by decreasing the L‐type Ca 2+ current (I Ca ) (1, 2). This effect is mediated via inhibition of adenylyl cyclase and subsequent reduction of cAMP‐dependent phosphorylation of voltage‐dependent L‐type Ca 2+ channels (3). Little is known, however, about the nature and origin of this pivotal inhibitory pathway. Using embryonic stem cells as an in vitro model of cardiomyogenesis, we found that muscarinic agonists depress I Ca by 58 ±3% ( n =34) in early stage cardiomyocytes lacking functional β ‐adrenoceptors. The cholinergic inhibition is mediated by the nitric oxide (NO)/cGMP system since it was abolished by application of NOS inhibitors (L‐NMA, L‐NAME), an inhibitor of the soluble guanylyl cyclase (ODQ), and a selective phosphodiesterase type II antagonist (EHNA). The NO/cGMP‐mediated I Ca depression was dependent on a reduction of cAMP/protein kinase A (PKA) levels since application of the catalytic subunit of PKA or of the PKA inhibitor PK) prevented the carbachol effect. In late development stage cells, as reported for ventricular cardiomyocytes (2, 4), muscarinic agonists had no effect on basal I Ca but antagonized β‐adrenoceptor‐stimulated I Ca by 43 ±4% ( n =16). This switch in signaling pathways during development is associated with distinct changes in expression of the two NO‐producing isoenzymes, eNOS and iNOS, respectively. These findings indicate a fundamental role for NO as a signaling molecule during early embryonic development and demonstrate a switch in the signaling cascades governing I Ca regulation.—Ji, G. J., Fleischmann, B. K., Bloch, W., Feelisch, M., Andressen, C., Addicks, K., Hescheler, J. Regulation of the L‐type Ca 2+ channel during cardiomyogenesis: switch from NO to adenylyl cyclase‐mediated inhibition. FASEB J. 13, 313–324 (1999)