Serotonin increases L-type Ca2+ current and SR Ca2+ content through 5-HT4 receptors in failing rat ventricular cardiomyocytes.
Rats with congestive heart failure (CHF) develop ventricular inotropic responsiveness to serotonin (5-HT), mediated through 5-HT(2A) and 5-HT(4) receptors. Human ventricle is similarly responsive to 5-HT through 5-HT(4) receptors. We studied isolated ventricular cardiomyocytes to clarify the effects of 5-HT on intracellular Ca(2+) handling. Left-ventricular cardiomyocytes were isolated from male Wistar rats 6 wk after induction of postinfarction CHF. Contractile function and Ca(2+) transients were measured in field-stimulated cardiomyocytes, and L-type Ca(2+) current (I(Ca,L)) and sarcoplasmic reticulum (SR) Ca(2+) content were measured in voltage-clamped cells. Protein phosphorylation was measured by Western blotting or phosphoprotein gel staining. 5-HT(4)- and 5-HT(2A)-receptor stimulation induced a positive inotropic response of 33 and 18% (both P < 0.05) and also increased the Ca(2+) transient (44 and 6%, respectively; both P < 0.05). I(Ca,L) and SR Ca(2+) content increased only after 5-HT(4)-receptor stimulation (57 and 65%; both P < 0.05). Phospholamban serine(16) (PLB-Ser(16)) and troponin I phosphorylation increased by 26 and 13% after 5-HT(4)-receptor stimulation (P < 0.05). 5-HT(2A)-receptor stimulation increased the action potential duration and did not significantly change the phosphorylation of PLB-Ser(16) or troponin I, but it increased myosin light chain 2 (MLC2) phosphorylation. In conclusion, the positive inotropic response to 5-HT(4) stimulation results from increased I(Ca,L) and increased phosphorylation of PLB-Ser(16), which increases the SR Ca(2+) content. 5-HT(4) stimulation is thus, like beta-adrenoceptor stimulation, possibly energetically unfavorable in CHF. 5-HT(2A)-receptor stimulation, previously studied in acute CHF, induces a positive inotropic response also in chronic CHF, probably mediated by MLC2 phosphorylation.
Institute for Experimental Medical Research, Ullevaal Univ. Hospital, Kirkeveien 166, 0407 Oslo, Norway. j.a.birkeland@medisin.uio.no
Jon Arne Kro
JA
Birkeland
Fredrik
F
Swift
Nils
N
Tovsrud
Ulla
U
Enger
Per Kristian
PK
Lunde
Eirik
E
Qvigstad
Finn Olav
FO
Levy
Ole M
OM
Sejersted
Ivar
I
Sjaastad
D000200:Action Potentials; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002135:Calcium-Binding Proteins / Q000378:metabolism; D024722:Cardiac Myosins; D002316:Cardiotonic Agents / Q000378:metabolism*; D003331:Coronary Vessels / Q000601:surgery; D004195:Disease Models, Animal; D006333:Heart Failure / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D007211:Indoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008026:Ligation; D008297:Male; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000150:complications / Q000378:metabolism / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D018994:Myosin Light Chains; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism; D044422:Receptors, Serotonin, 5-HT4 / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D058830:Serotonin 5-HT2 Receptor Antagonists; D058832:Serotonin 5-HT4 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D019210:Troponin I / Q000378:metabolism; D016276:Ventricular Function / Q000187:drug effects; D000099211:Phospholamban
D000318:Adrenergic beta-Agonists; D020746:Calcium Channels, L-Type; D002135:Calcium-Binding Proteins; D024722:Cardiac Myosins; D002316:Cardiotonic Agents; D007211:Indoles; D007545:Isoproterenol; D007650:Ketanserin; D018994:Myosin Light Chains; D044402:Receptor, Serotonin, 5-HT2A; D044422:Receptors, Serotonin, 5-HT4; D012701:Serotonin; D058830:Serotonin 5-HT2 Receptor Antagonists; D058832:Serotonin 5-HT4 Receptor Antagonists; D012702:Serotonin Antagonists; D013449:Sulfonamides; D019210:Troponin I; D000099211:Phospholamban; C107184:myosin light chain 2; C082871:GR 113808