Leukotriene C4 receptors in cultured smooth muscle cells from bovine anterior cerebral arteries and microcerebrovasculatures

Specific receptors for leukotriene C4 (LTC4) were identified on smooth muscle cells isolated from bovine anterior cerebral arteries (BACASMC) and bovine microcerebrovasculatures (BMSMC). [3H]LTC4 specific bindings to both cells at a fixed input reached the maxima at 60 min and 20 min, respectively. With incremental inputs of radioligand and a constant cell number, [3H]LTC4 specific bindings reached a plateau indicative of a saturable binding site. Analysis of Scatchard plots demonstrated a single population of high-affinity binding sites in both cells. The dissociation constant (Kd) for BACASMC was 39.2 +/- 1.3 nmol.L-1 and its Bmax was 19.3 +/- 2.1 pmol/10(6) cells. For BMSMC, Kd = 2.0 +/- 0.4 nmol.L-1, Bmax = 157 +/- 13 fmol/10(6) cells. The specific [3H]LTC4 bindings was inhibited by unlabeled LTC4, LTD4 and FPL-55712 (an SRS-A antagonist). The inhibitory rates for BACASMC were 70.4% and 35.3% by LTC4 and FPL-55712 at 1 mumol.L-1, respectively. For BMSMC the inhibitory rates were 96.9%, 73.9%, and 44.9% by LTC4, LTD4, and FPL-55712 at 10 mumol.L-1, respectively.