title: Electrophysiology of phagocytic membranes. Role of divalent cations in membrane hyperpolarizations of macrophage polykaryons.
abstract: The electrophysiological properties of the membrane of mouse peritoneal macrophage polykaryons are studied. Slow hyperpolarizations can be elicited by iontophoretic injections of either Ca2+ or Sr2+ into the cytoplasm. The effect of both cations is identical, since: it is invariably triggered by the cation injection, the amplitude is dependent on the K+ gradient, quinine blocks reversibly the response to both cation injections. Mg2+, Ba2+ and Mn2+ did not elicit responses when injected into the cytoplasm. Ca2+ induced slow hyperpolarizations were reversibly blocked by the addition of Ba2+ to the external saline, but were not affected by the presence of external tetraethylammonium chloride. Cells maintained in saline containing high concentrations of Ca2+, Sr2+ or Mn2+ exhibited sustained hyperpolarizations. Quinine blocked the hyperpolarization induced by high Ca2+ or Sr2+, but was ineffective for the case of Mn2+. Cells hyperpolarized by external Mn2+ frequently exhibited nonlinear, voltage-current characteristics. Similar patterns could also be observed in a small fraction (less than 10%) of the cells in control conditions. Current-induced shifts between two stable membrane potentials were seen either in high Ca2+ or normal medium. The great variability of the responses described for this phagocytic membrane is discussed. The evidence supports the assumption that Ca2+ and Sr2+ can induce transient or persistent hyperpolarized states by activating a potassium permeability. External Mn2+ may act in part by reducing impalement-related current leakage from the phagocytic membrane.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent; D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity / Q000187:drug effects; D007700:Kinetics; D008264:Macrophages / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008806:Mice, Inbred AKR; D008809:Mice, Inbred C3H; D010587:Phagocytosis; D011803:Quinine / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D001464:Barium; D008345:Manganese; D011803:Quinine; D008274:Magnesium; D002118:Calcium; D013324:Strontium