title: Effect of antihistamines and chlorpromazine on the calcium-induced hyperpolarization of the Amphiuma red cell membrane.
abstract: 1. It has previously been demonstrated that an increase in extracellular Ca2+ conce-tratio- induces a trandient increase in K+ permeability and associated hyperpolarization of the red cell membrane of the giant salamander, Amphiuma meand. This phenomenon is analogous to the Ca2+-induced KCl loss observed in ATP-depleted human red cells and red cell ghosts. 2. Histamine, which enhances the Ca2+-induced K+ loss from depleted human red cells, is without effect on this Ca2+-induced hyperpolarization of Amphiuma red cells. 3. Promethazine (10 muM) and mepyramine (1 mM), which inhibit the Ca2+-induced K+ loss in depleted human red cells, also block the Ca2+-related hyperpolarization of Amphiuma erythrocytes. 4. Chlorpromazine (25 muM), despite being a weak antihistamine, is equally effective in blocking the Ca2+-induced hyperpolarization of Amphiuma red cells. 5. Ionophore A23187 causes a large and sustained Ca2+/K+-dependent hyperpolarization even in the presence of normal (1.8 mM) concentrations of Ca2+. This hyperpolarization is relatively insensitive to chlorpromazine and promethazine. 6. The inhibition of the Ca2+-induced hyperpolarization of the Amphiuma red cell membrane by chlorpromazine and promethazine may berelated to their properties as local anaesthetics.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood / Q000494:pharmacology*; D002463:Cell Membrane Permeability; D002746:Chlorpromazine / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000502:physiology*; D004912:Erythrocytes / Q000502:physiology*; D006632:Histamine / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D011398:Promethazine / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D011738:Pyrilamine / Q000494:pharmacology*; D014562:Caudata
chemical_list: D011725:Pyridines; D000001:Calcimycin; D006632:Histamine; D011398:Promethazine; D011738:Pyrilamine; D011188:Potassium; D002118:Calcium; D002746:Chlorpromazine