Characterization of leukotriene C4 binding sites in the brain of the American bullfrog,Rana catesbeiana

✍ Scribed by Herman, Ceil A. ;Charlton, Gregory A. ;Chiono, Matt

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 791 KB
• Volume: 262
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402620102

✦ Synopsis

Abstract

In this study, specific binding sites for [^3^H]‐LTC~4~ on membrane preparations from American bullfrog (Rana catesbeiana) brain were characterized. Binding assays were done in the presence of serine (5mM) borate (10 mM) for 30 min at 23°C. Under these conditions, no metabolism of LTC~4~ to LTD~4~ occurred. Specific binding of [^3^H]‐LTC~4~ reached steady state within 10 min, remained constant for 60 min, and was reversible with the addition of 1,000‐fold excess unlabelled LTC~4~. Scatchard analysis of the binding data indicated a single class of binding sites with an estimated K~d~ of 89.83 nM and B~max~ of 43.79 pmol/mg protein. Competition binding studies demonstrated that LTD~4~ and LTE~4~ were ineffective in displacing [^3^H]‐LTC~4~ from its binding site. The K~i~ for LTC~4~ was 51 nM. S‐decylglutathione, glutathione and hematin had K~i~ values of 44, 312,602, and 25,576 nM, respectively. The mammalian cysteinyl leukotriene antagonist L‐660,711 inhibited specific binding of [^3^H]‐LTC~4~, with a K~i~ of 87,149 nM. Guanosine‐5′‐0‐3‐thiotriphosphate (GTPγS) did not affect specific binding of [^3^H]‐LTC~4~ indicating that, like mammalian LTC~4~ receptors, a G~i~ protein is not involved in the transduction mechanism. The LTC~4~ binding site in bullfrog brain demonstrates both similarities and differences from its mammalian counterpart. © 1992 Wiley‐Liss, Inc.