Investigation of histamine-antihistamine differentiation ability of Tetrahymena receptors, by means of lectins and antihistamine antibodies.

Histamine antagonists bind to the histamine receptors of Tetrahymena, and their presence can be shown by immunocytofluorimetry. The binding of histamine is inhibited by antagonists structurally similar to histamine, regardless whether they bind to H1 or H2 receptors, but it is not inhibited by phenindamine, a compound structurally highly different from histamine. That part of H1 receptor which binds to both concanavalin A (con-A) and histamine probably contains primarily simple sugars, and secondly, glycosamine oligomers. At the H2 binding sites, on the other hand, acetylgalactosamine and its derivatives dominate. The present findings in the light of earlier functional experiments, suggest that in Tetrahymena, binding and effect are separated from each other to a certain degree.