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.
Birkeland
Jon Arne Kro
JA
Institute for Experimental Medical Research, Ullevaal Univ. Hospital, Kirkeveien 166, 0407 Oslo, Norway. j.a.birkeland@medisin.uio.no
Swift
Fredrik
F
Tovsrud
Nils
N
Enger
Ulla
U
Lunde
Per Kristian
PK
Qvigstad
Eirik
E
Levy
Finn Olav
FO
Sejersted
Ole M
OM
Sjaastad
Ivar
I
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