Calcium is necessary but not sufficient for the platelet-activating factor release in human neutrophils stimulated by physiological stimuli. Role of G-proteins.
Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine; PAF) enhances the release of newly synthesized PAF as measured by [3H]acetate incorporation into PAF in human neutrophils. The response was dose-dependent, rapid, transient, and inhibitable by the PAF antagonist BN-52021. The non-metabolizable bioactive PAF analogue (C-PAF) but not lyso-PAF enhances the release of newly synthesized PAF. Newly synthesized PAF was also released after stimulation of these cells with fMet-Leu-Phe. The human granulocyte-macrophage colony-stimulating factor potentiates the stimulated release of PAF. The intracellular calcium chelator BAPTA inhibits the rise of [Ca2+]i and the release of PAF but not the Na+/H+ antiport activity. PAF release, but not the rise in the intracellular concentration of free calcium, was inhibited in pertussis toxin-treated neutrophils stimulated with PAF. The release of PAF in pertussis toxin-treated cells was also inhibited in cells stimulated with fMet-Leu-Phe or opsonized zymosan. These results suggest that functional pertussis toxin-sensitive guanine nucleotide regulatory protein and/or one or more of the changes produced by phospholipase C activation are necessary for PAF release produced by physiological stimuli. It appears that PAF release requires a coordinated action of receptor-coupled G-proteins, calcium, and other parameters.
Gomez-Cambronero
J
J
Department of Physiology, University of Connecticut Health Center, Farmington 06032.
Durstin
M
M
Molski
T F
TF
Naccache
P H
PH
Sha'afi
R I
RI
D003115:Colony-Stimulating Factors / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D019204:GTP-Binding Proteins / Q000097:blood* / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D015290:Second Messenger Systems / Q000187:drug effects; D015054:Zymosan / Q000494:pharmacology
D003115:Colony-Stimulating Factors; D006133:Growth Substances; D010972:Platelet Activating Factor; D004533:Egtazic Acid; D009240:N-Formylmethionine Leucyl-Phenylalanine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D015054:Zymosan; D019204:GTP-Binding Proteins; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid