Characterization of histamine type 1 receptors on natural suppressor lymphoid cells

Using the radioligand H1 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 H1 receptor antagonists. The rank order of potency for displacement of [3H]pyrilamine binding from the H1 receptor by H1 receptor antagonists was promethazine = pyrobutamine greater than pyrilamine greater than diphenhydramine greater than 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 KD was 1.1 +/- 0.3 X 10(-7) M while the measured KD of binding for [3H]pyrilamine was 6.0 +/- 0.8 X 10(-8) M; the maximum binding was 4.13 nM and the number of binding sites/cell was 2.14 +/- 0.29 X 10(6) (N = 3).