CHARACTERISTICS OF HISTAMINE-H(1) RECEPTORS ON HELA-CELLS

The affinities of antagonists at histamine H-1 receptors on HeLa cells have been determined from inhibition of histamine-induced inositol phosphate formation in intact cells and from inhibition of [H-3]mepyramine binding to HeLa cell membranes. The dissociation constants of mepyramine and (+)-chlorpheniramine were similar to values for binding to H-1 receptors in other mammalian tissues, but much lower than the values reported in an earlier study with [H-3]mepyramine and HeLa cell membranes. Evidence is presented that under the conditions employed in the earlier study the binding of [H-3]mepyramine is largely to secondary, non-H-1 receptor sites.