BACKGROUND AND AIMS The liver is a major site for the synthesis and actions of platelet activating factor (PAF), a potent hepatic vasoconstrictor and systemic vasodilator. As PAF is implicated in portal hypertension and hyperdynamic circulation associated with liver cirrhosis, we characterised changes in the hepatic PAF system in experimental cirrhosis. METHODS In rats made cirrhotic by carbo...

Prolonged exposure (8-24 h) of human promonocytic U937 cells to 100 nM 1-O-hexadecyl-2-N-methylcarbamyl-sn-glycero-3-phosphocholine (carbarmyl-PAF), a non-metabolizable analogue of platelet-activating factor (PAF), reduced the numbers of PAF receptors by 50-75%, as determined by the radioligand-binding assay. To clarify whether the down-regulation of receptor numbers is due to decreased express...

During inflammation polymorphonuclear cells (PMNs) are exposed to agonistic stimuli including activated complement, kallikrein, arachidonic acid metabolites, monokines, and platelet-activating factor (PAF). We report that PAF not only directly activates PMNs but in miniscule quantities (10(-12) mol/L) "primes" them as well, that is, permits PMNs to respond to subsequent stimuli that would be ot...

The effect of lyso-PAF on ciliated cells was investigated in vitro. Normal mucosa was surgically obtained from human paranasal sinuses and incubated in the form of tissue culture. Ciliated epithelium was magnified under an inverted microscope, and ciliary movement was photo-electrically measured. Ciliary activity was significantly inhibited by 10(-8) M lyso-PAF and could be restored. The effect...

The object of this study was to characterize the synthesis and metabolism of platelet activating factor (PAF) by intestinal mucosa subjected to ischaemia-reperfusion injury. Canine intestinal mucosa produced 16:0-PAF, 18:0-PAF, and high levels of the corresponding lyso- PAF metabolites. Three h of intestinal ischaemia and ischaemia followed by 1 h of reperfusion did not affect the synthesis or ...

Platelet-activating factor (PAF) is one of the most potent lipid mediators involved in inflammatory events. The acetyl group at the sn-2 position of its glycerol backbone is essential for its biological activity. Deacetylation induces the formation of the inactive metabolite lyso-PAF. This deacetylation reaction is catalyzed by PAF-acetylhydrolase (PAF-AH), a calcium independent phospholipase A...

PURPOSE Platelet activating factor (PAF) is a potent inflammatory mediator the synthesis of which increases in the cornea after injury. The effects of PAF are mediated by receptors (PAF-R), which are present in target cells. This study was undertaken to investigate the effects of wound healing, PAF, and growth factors on modulating PAF-R mRNA levels in corneal epithelial cells. METHODS Cultur...

Platelet-activating factor (PAF) desensitizes as well as stimulates its various target cells, We find that human polymorphonuclear neutrophils (PMN) exposed to PAF became maximally unresponsive to a second PAF challenge within 15-90 s in assays of Ca2+ mobilization and degranulation. The cells regained full PAF-sensitivity over the ensuing 20-40 min. These effects correlated with changes in PAF...

BACKGROUND Platelet-activating factor (PAF) is a phospholipid that has been implicated in the pathogenesis of glomerulonephritis and can be synthesized by glomerular cells in response to different stimuli. PAF increases glomerular permeability to proteins and urinary PAF has been determined to be of renal origin. In order to assess whether urinary PAF can be found augmented in situations of glo...