title: Radioimmunoassay of LTB4 in plasma from different species: a cautionary note.
abstract: In clinical and pre-clinical research the pharmacodynamics of selective 5-lipoxygenase and dual 5-lipoxygenase/cyclo-oxygenase inhibitors may be studied by direct RIA of plasma LTB4. Although immunoreactive LTB4 in plasma from A23187 stimulated human blood has the characteristics of authentic LTB4 our results show, particularly in mice and rats, that exposure to A23187 produces large quantities of 12-HETE. Since in different species the levels of 12-HETE increase with platelet concentration we suggest that the 12(S)-HETE is produced by platelet lipoxygenase. However, we do not rule out the possibility that a proportion of 12-HETE may exist as the (R)-stereoisomer. The latter has greater potential for interference in the direct RIA of LTB4. Biosynthesis of 12-HETE may be measured either by RPHPLC/U.V. abs. (8) or by RIA (9) and LTB4 by a more specific antibody described in this report. We conclude that the combined ex vivo RIA of plasma TXB2, LTB4 and 12-HETE has utility in determining the selectivity of inhibitors of arachidonate metabolism and in distinguishing between selective 5-lipoxygenase inhibitors which interact directly with the enzyme and anti-oxidant or free radical scavenging types which may be less specific.
authors.affiliation: Research Department II, ICI Pharmaceuticals, Macclesfield, Cheshire, UK.
authors.forename: F
authors.initials: F
authors.lastname: Carey
authors.forename: R A
authors.initials: RA
authors.lastname: Forder
authors.forename: K H
authors.initials: KH
authors.lastname: Gibson
authors.forename: D
authors.initials: D
authors.lastname: Haworth
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003429:Cross Reactions; D016861:Cyclooxygenase Inhibitors; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood* / Q000302:isolation & purification; D007975:Leukotriene B4 / Q000097:blood* / Q000302:isolation & purification; D016859:Lipoxygenase Inhibitors; D051379:Mice; D011863:Radioimmunoassay; D051381:Rats; D013045:Species Specificity; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D016861:Cyclooxygenase Inhibitors; D006893:Hydroxyeicosatetraenoic Acids; D016859:Lipoxygenase Inhibitors; D007975:Leukotriene B4; D000001:Calcimycin; D013929:Thromboxane B2; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid