Chloride channels in brown adipocyte plasma membranes: candidates for mediation of alpha 1-adrenergic depolarization?
The presence of plasma membrane Cl- channels was investigated in brown-fat cells differentiated in culture. Single channel activity was followed by the patch-clamp technique, with an NMDG+ Cl- pipette solution and a NaCl bath solution. Only rarely was putative Cl- channel activity encountered in the cell-attached mode. However, after excision, ion channel activity of two types was observed in inside-out patches: one type represented the earlier observed non-selective cation channel, and one a putative Cl- channel, with the following characteristics: practically non-rectifying current-voltage relationship with a conductance of approximately 50 pS and a reversal potential of approximately 0 in symmetrical Cl- solutions, voltage dependent channel activity (Po approached 0.5 at positive holding potentials), and rapid flickering activity in the open state. It is discussed whether this Cl- channel may be responsible for the initial depolarization phase observed after alpha 1-adrenergic stimulation of brown-fat cells.
Sabanov
V
V
Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, Sweden.
Nedergaard
J
J
D002001:Adipose Tissue, Brown / Q000166:cytology / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D004558:Electric Stimulation; D008536:Meglumine / Q000494:pharmacology*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D018408:Patch-Clamp Techniques; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors
D018118:Chloride Channels; D002712:Chlorides; D018340:Receptors, Adrenergic, alpha-1; D012965:Sodium Chloride; D008536:Meglumine