Mutual contact of murine erythroleukemia cells activates depolarizing cation channels, whereas contact with extracellular substrata activates hyperpolarizing Ca2+-dependent K+ channels.
This study deals with the modulation of the plasma membrane potential (delta psi p) of murine erythroleukemia (MEL) cells by cell-substratum or cell-cell contact. delta psi p was determined by measuring the distribution of tetraphenylphosphonium (TPP+) across the plasma membrane; it appeared strongly, and inversely, influenced by the two types of cell contacts. Contact with the culture surface produced a delta psi p hyperpolarization directly proportional to average distance among the ideal centers of the cells on this surface (d) within the range 10-80 microns. A detailed mathematical analysis of the function delta psi p = f(d) is presented, as well as experiments involving the use of ionophores (valinomycin and A23187) and the conditioning of the culture surface. We concluded that the d-dependent hyperpolarization (dDH) was the result of a complex interplay between the activating properties of substratum on Ca2+-dependent K+ channels (KCa) and some substratum-adherent factors that are shed by MEL cells and antagonize KCa activation (substratum-attached cellular factors = SACF). By contrast, contact of the cells with each other, obtained by incubating MEL cells at d smaller than the average cell diameter (phi = 10 microns), produced a marked delta psi p depolarization. This intercellular contact-dependent depolarization (ICDD) was unaffected by valinomycin; it was abolished by substituting Na+ in the external medium with a nondiffusible cation (choline), which shows that ICDD was sustained by Na+ influxes, probably mediated by stretch-activated (s.a.) cation channels.
Arcangeli
A
A
Institute of General Pathology, Medical Faculty, University of Florence, Firenze, Italy.
Riccarda Del Bene
M
M
Poli
R
R
Ricupero
L
L
Olivotto
M
M
D000818:Animals; D001696:Biomechanical Phenomena; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002412:Cations / Q000378:metabolism*; D002450:Cell Communication; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D007477:Ions; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D015221:Potassium Channels / Q000502:physiology*; D012964:Sodium / Q000502:physiology; D014634:Valinomycin / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D007477:Ions; D015221:Potassium Channels; D014634:Valinomycin; D000001:Calcimycin; D012964:Sodium; D002118:Calcium