Characterization of histamine type 1 receptors on natural suppressor lymphoid cells

Abstract

Using the radioligand H 1 antagonist [ 3H]pyrilamine, we have characterized the histamine type 1 receptor on cloned murine natural suppressor cells (NS). A single, specific binding site for [ 3H]pyrilamine exists on these cells. The binding was saturable and reversible by various specific H 1 receptor antagonists. The rank order of potency for displacement of [ 3H]pyrilamine binding from the H 1 receptor by H 1 receptor antagonists was promethazine = pyrobutamine > pyrilamine > diphenhydramine > chlorpheniramine. The histamine type-2 agonists, impromidine and dimaprit, and antagonists, cimetidine and ranitidine, as well as selected non-histamine agonists, did not displace [ 3H]pyrilamine from its binding sites on the natural suppressor cells. The data indicate that the theoretical K D was 1.1 ± 0.3 × 10 −7M while the measured K D of binding for [ 3H]pyrilamine was 6.0 ± 0.8 × 10 −8M; the maximum binding was 4.13 nM and the number of binding sites/cell was 2.14 ± 0.29 × 10 6 (N = 3).