Characteristics of [3H]mepyramine binding in DDT1MF-2 cells: evidence for high affinity binding to a functional histamine H1 receptor.
The binding characteristics of [3H]mepyramine to histamine H1 receptors in the smooth muscle cell line, DDT1MF-2, have been investigated. Competition binding experiments produced dissociation constants (Ki) for mepyramine, (+)-chlorpheniramine, and promethazine of 3.4 nM, 2.6 nM and 0.66 nM, respectively. Saturation binding using [3H]mepyramine produced a Kd of 2.1 nM and a Bmax of 47 fmol/mg protein. These data suggest that a high-affinity [3H]mepyramine binding site can be detected with the characteristics of the "classical" histamine H1 receptor. The low-affinity [3H]mepyramine binding site reported previously [Mitsuhashi, M. and Payan, D.G. (1988) J. Cell. Physiol. 134, 367-375] is predominantly to a secondary [3H]mepyramine site. The "low affinity" or secondary [3H]mepyramine binding site on DDT1MF-2 cells is insensitive to quinine (10 microM) and is therefore distinct from the [3H]mepyramine binding protein found in rat liver.
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, UK.
J M
JM
Dickenson
S J
SJ
Hill
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D006224:Cricetinae; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D011738:Pyrilamine / Q000378:metabolism*; D011803:Quinine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000378:metabolism*; D014649:Vas Deferens / Q000378:metabolism
D011969:Receptors, Histamine H1; D011803:Quinine; D011738:Pyrilamine