Development of a radioimmunoassay for 15-HETE and its application to 15-HETE production by reticulocytes.
Mono-hydroxy-eicosatetraenoic acids (HETE's) are frequently the principal lipoxygenase-derived products in a number of cell types. This paper describes the development of a selective and sensitive radioimmunoassay procedure for 15-HETE, a metabolite which has previously been shown to be both an activator and inhibitor of leukotriene formation in various cells. Initially, rabbits were immunized with 15-HETE conjugated to bovine serum albumin. After seven months, the anti-plasma showed significant binding of tritiated 15-HETE (40-45% binding with a 1:600 dilution of the anti-plasma) which was displaceable by cold 15-HETE. The sensitivity of the assay was approximately 20 pg. of 15-HETE. The anti-plasma exhibited very little (less than 1%) cross-reactivity with arachidonic acid, 5-, 8-, 9-, 11- and 12-HETE's, HHT, TXB2, PGE2 and 6-Keto-PGF1 alpha. Significant cross-reactivity was observed with 5,15-diHETE (53%), 8, 15-diHETE (6.6%), and several other 15-hydroxy-eicosanoids. Rabbit reticulocytes have a very active 15S-lipoxygenase and converted arachidonic acid (final concentration 7 microM) principally to 15-HETE. Unstimulated reticulocytes were found to release negligible amounts of 15-HETE as determined by radioimmunoassay. Treatment of these cells with the calcium ionophore A23187 (0.16 to 4.0 micrograms/ml) elicited a level of 15-HETE release (8 - 14 ng/ml) that was twenty to forty times less than that obtained with exogenous arachidonic acid (2.5 micrograms/ml). The radioimmunoassay reported here may be useful for identifying factors which stimulate cellular release of 15-HETE and other 15-hydroxy-eicosanoids from endogenous arachidonic acid.
D000818:Animals; D001095:Arachidonic Acids / Q000032:analysis*; D000001:Calcimycin / Q000494:pharmacology; D003429:Cross Reactions; D006893:Hydroxyeicosatetraenoic Acids; D011817:Rabbits; D011863:Radioimmunoassay / Q000379:methods; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism*; D013929:Thromboxane B2 / Q000378:metabolism; D013997:Time Factors
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D000001:Calcimycin; D013929:Thromboxane B2; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid