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cAMP‐ and Ca 2+ /calmodulin‐dependent protein kinases mediate inotropic, lusitropic and arrhythmogenic effects of urocortin 2 in mouse ventricular myocytes
Author(s) -
Yang LiZhen,
Kockskämper Jens,
Khan Shelina,
Suarez Jorge,
Walther Stefanie,
Doleschal Bernhard,
Unterer Gregor,
Khafaga Mounir,
Mächler Heinrich,
Heinzel Frank R.,
Dillmann Wolfgang H.,
Pieske Burkert,
Spiess Joachim
Publication year - 2011
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2010.01067.x
Subject(s) - urocortin , phospholamban , medicine , endocrinology , lusitropy , protein kinase a , chemistry , myocyte , receptor , contractility , phosphorylation , biology , calcium , biochemistry , diastole , blood pressure
BACKGROUND AND PURPOSE Urocortin 2 is beneficial in heart failure, but the underlying cellular mechanisms are not completely understood. Here we have characterized the functional effects of urocortin 2 on mouse cardiomyocytes and elucidated the underlying signalling pathways and mechanisms. EXPERIMENTAL APPROACH Mouse ventricular myocytes were field‐stimulated at 0.5 Hz at room temperature. Fractional shortening and [Ca 2+ ] i transients were measured by an edge detection and epifluorescence system respectively. Western blots were carried out on myocyte extracts with antibodies against total phospholamban (PLN) and PLN phosphorylated at serine‐16. KEY RESULTS Urocortin 2 elicited time‐ and concentration‐dependent positive inotropic and lusitropic effects (EC 50 : 19 nM) that were abolished by antisauvagine‐30 (10 nM, n = 6), a specific antagonist of corticotrophin releasing factor (CRF) CRF 2 receptors. Urocortin 2 (100 nM) increased the amplitude and decreased the time constant of decay of the underlying [Ca 2+ ] i transients. Urocortin 2 also increased PLN phosphorylation at serine‐16. H89 (2 µM) or KT5720 (1 µM), two inhibitors of protein kinase A (PKA), as well as KN93 (1 µM), an inhibitor of Ca 2+ /calmodulin‐dependent protein kinase II (CaMKII), suppressed the urocortin 2 effects on shortening and [Ca 2+ ] i transients. In addition, urocortin 2 also elicited arrhythmogenic events consisting of extra cell shortenings and extra [Ca 2+ ] i increases in diastole. Urocortin 2‐induced arrhythmogenic events were significantly reduced in cells pretreated with KT5720 or KN93. CONCLUSIONS AND IMPLICATIONS Urocortin 2 enhanced contractility in mouse ventricular myocytes via activation of CRF 2 receptors in a cAMP/PKA‐ and Ca 2+ /CaMKII‐dependent manner. This enhancement was accompanied by Ca 2+ ‐dependent arrhythmogenic effects mediated by PKA and CaMKII.