Leukotriene C4 binding sites in mouse brain: pharmacological characteristics

The binding sites for [3H]leukotriene C4 were studied in membrane preparations of mouse brain and liver. Isotherm binding analysis revealed one binding site with a Kd of 10.39 +/- 1.97 nM (Scatchard) or 10.15 +/- 1.00 nM (non-linear). The maximal binding capacity (Bmax) was 49.20 +/- 3.80 (Scatchard) or 48.50 +/- 2.63 (non-linear) pmol/mg prot. Specific binding represented more than 90% of the total binding. In displacement reactions on brain membranes, LTC4 was 100 times more active than LTD4, which displayed 10 times the activity of GSH. Glutamic acid, bilirubin and hematin were inactive. The activity of LTC4 was slightly less on liver membranes than on brain membranes. Liver sites had some affinity for GSH but not for LTD4 bilirubin or hematin. The results support the hypothesis that LTC4 and its receptor may have a neuromodulatory function.