title: Occurrence of an endogenous inhibitor of platelet-activating factor in rat liver.
abstract: Hepatocytes obtained from livers derived from fed rats perfused with a collagenase-containing mixture were found to contain significant levels of platelet-activating factor activity as isolated by Silica Gel G thin layer chromatography. However, when soybean trypsin inhibitor was included in the collagenase-containing perfusion medium for hepatocyte preparation, platelet-activating factor activity could not be detected on Silica Gel G chromatograms. Examination of the lipids extracted from freeze clamped perfused rat livers revealed low, but detectable, levels of platelet-activating factor. Further investigation of these observations indicated that a lipid-like inhibitor was present in freeze-clamped perfused livers as well as in hepatocytes isolated in the presence of soybean trypsin inhibitor. In each instance platelet-activating factor and this newly discovered inhibitor, which comigrated at the same RF value on Silica Gel G thin layer chromatography plates, could be separated by further chromatography on high performance thin layer plates. The present study shows that platelet-activating factor is present in unstimulated liver and that its detection is masked by an endogenous lipid-like inhibitor.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008055:Lipids / Q000302:isolation & purification* / Q000494:pharmacology; D008099:Liver / Q000502:physiology*; D008297:Male; D010477:Perfusion; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D011817:Rabbits; D051381:Rats; D012701:Serotonin / Q000097:blood
chemical_list: D008055:Lipids; D010972:Platelet Activating Factor; D012701:Serotonin