Radioimmunoassay of LTB 4 in plasma from different species: A cautionary note

• Published in: Prostaglandins, leukotrienes and essential fatty acids Vol. 36; no. 1; pp. 57 - 61
• Main Authors: Carey, F., Forder, R.A., Gibson, K.H., Haworth, D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1989
• ISSN: 0952-3278; 1532-2823
• DOI: 10.1016/0952-3278(89)90163-4

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 LTB 4. Although immunoreactive LTB 4 in plasma from A23187 stimulated human blood has the characteristics of authentic LTB 4 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 LTB 4. Biosynthesis of 12-HETE may be measured either by RPHPLC U.V. abs. (8) or by RIA (9) and LTB 4 by a more specific antibody described in this report. We conclude that the combined ex vivo RIA of plasma TXB 2, LTB 4 and 12-HETE has utility in determining the selectivity of inhibitors of archidonate 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.