Functional and biochemical characterization of immunologically derived equine platelet-activating factor

• Published in: Veterinary pathology Vol. 22; no. 4; p. 375
• Main Authors: Wimberly, H.C, Slauson, D.O, Neilsen, N.R
• Format: Journal Article
• Language: English
• Published: United States 01.07.1985
• Subjects: acetyl glyceryl phosphorylcholine; Animals; Antigens, Helminth - immunology; Ascaris - immunology; Aspirin - pharmacology; BIOCHEMISTRY; BIOCHIMIE; BIOQUIMICA; Blood Platelets - drug effects; Blood Platelets - secretion; CABALLOS; CHEVAL; Chromatography, Thin Layer; Dose-Response Relationship, Drug; Female; HORSES; Horses - physiology; IMMUNOLOGIE; IMMUNOLOGY; In Vitro Techniques; Indomethacin - pharmacology; INMUNOLOGIA; L-Lactate Dehydrogenase - metabolism; LEUCOCITOS; LEUCOCYTE; LEUKOCYTES; Leukocytes - immunology; Leukocytes - metabolism; Male; Platelet Activating Factor - analysis; Platelet Activating Factor - pharmacology; Platelet Activating Factor - physiology; Platelet Aggregation; PLATELETS; Serotonin - secretion; THROMBOCYTE; TROMBOCITOS
• ISSN: 0300-9858; 1544-2217
• DOI: 10.1177/030098588502200413

Antigen-specific challenge of equine leukocytes induced the non-lytic release of a platelet-activating factor in vitro. The equine platelet-activating factor stimulated the release of serotonin from equine platelets in a dose-responsive manner, independent of the presence of cyclo-oxygenase pathway inhibitors such as indomethacin. Rabbit platelets were also responsive to equine platelet-activating factor. The release of equine platelet-activating factor was a rapid reaction with near maximal secretion taking place in 30 seconds. Addition of equine platelet-activating factor to washed equine platelets stimulated platelet aggregation which could not be inhibited by the presence of aspirin or indomethacin. Platelets pre-incubated with equine platelet-activating factor became specifically desensitized to equine platelet-activating factor while remaining responsive to other platelet stimuli such as collagen and epinephrine. The following biochemical properties of equine platelet-activating factor are identical to those properties of 1-0-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC): stability upon exposure to air and acid; loss of functional activity after base-catalyzed methanolysis with subsequent acylation that returned all functional activity; and identical relative mobilities on silica gel G plates developed with chloroform:methanol:water (65:35:6, volume/volume). The combined functional and biochemical characteristics of equine platelet-activating factor strongly suggest identity between this naturally occurring, immunologically derived equine factor and AGEPC.