title: Effects of platelet-activating factor on intracellular Ca2+ concentration and contractility in isolated cardiomyocytes.
abstract: We investigated the effects of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) on intracellular Ca2+ concentration ([Ca2+]i) and cell length in isolated and field-stimulated rat cardiomyocytes. [Ca2+]i and cell length of field-stimulated cells were determined simultaneously by confocal laser scan microscopy by using the fluorescent Ca2+ dye Fluo-3. PAF (10(-12)-10(-8) M) inhibited systolic [Ca2+]i increase in a time- and concentration-dependent manner. Maximal effects were observed after an incubation time of 6-8 min, resulting in a 17% (10(-12) M), 41% (10(-10) M), and 52% (10(-8) M PAF) inhibition of systolic [Ca2+]i increase. A time- and concentration-dependent decrease in simultaneously measured cell shortening also was demonstrated. Cell shortening was inhibited by 10% (10(-12) M), 32% (10(-10) M), and 50% (10(-8) M) after an incubation time of 8 min. The effects of PAF could be antagonized by the PAF-receptor antagonist WEB 2170. These data demonstrate that PAF receptor-dependently induces a negative inotropic effect, which is correlated with a decrease in systolic [Ca2+]i and is most likely not due to a decrease in myofilament sensitivity.
authors.affiliation: Medizinische Klinik I, Universitätsklinikum Charité, Humboldt-Universität zu Berlin, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Pietsch
authors.forename: T
authors.initials: T
authors.lastname: Hunger
authors.forename: M
authors.initials: M
authors.lastname: Braun
authors.forename: A
authors.initials: A
authors.lastname: Roediger
authors.forename: G
authors.initials: G
authors.lastname: Baumann
authors.forename: S B
authors.initials: SB
authors.lastname: Felix
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014230:Triazoles / Q000494:pharmacology
chemical_list: D001381:Azepines; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D014230:Triazoles; C063964:bepafant; D002118:Calcium