Ion channels in basolateral membrane of marginal cells dissociated from gerbil stria vascularis

• Published in: Hearing research 1995-03, Vol.83 (1), p.89-100
• Main Authors: Takeuchi, Shunji, Ando, Motonori, Kozakura, Kenichi, Saito, Haruo, Irimajiri, Akihiko
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - pharmacology; Adenosine Triphosphate - pharmacology; Animals; Biological and medical sciences; Bromides - metabolism; Calcium - pharmacology; Chlorides - metabolism; Cl − channel; Dose-Response Relationship, Drug; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Electric Conductivity; Fundamental and applied biological sciences. Psychology; Gerbillinae; Iodides - metabolism; Ion Channels - physiology; Ion transport; Marginal cell; Mathematics; Microscopy, Electron; Nitrates - metabolism; Nonselective cation channel; Patch-Clamp Techniques; Potassium - metabolism; Quaternary Ammonium Compounds - metabolism; Rubidium - metabolism; Sodium - metabolism; Stria Vascularis - cytology; Stria Vascularis - drug effects; Stria Vascularis - ultrastructure; Vertebrates: nervous system and sense organs
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/0378-5955(94)00191-R

The basolateral membrane of isolated strial marginal cells has been probed for conductive pathways by the patch-clamp technique. Two types of voltage-insensitive channels were identified in both cell-attached and excised patches. Of these, frequently (69% of excised patches) observed was a Ca 2+-activated nonselective cation channel having a unit conductance of 24.9 ± 0.5 pS ( N = 16). Other characteristics of this type in excised patches include: 1) linear I-V relations with 150 mM K + (pipette)/150 mM Na + (bath), 2) a permeability sequence of NH 4 +> Na + = K + = Rb +>Li +, 3) a flickering block by quinine or quinidine (both 1 mM), and 4) a dose dependent block of its activity by ADP or ATP (IC 50,ATP/IC 50,ADP = 20–35), both from the cytosolic side. Channels with similar characteristics were found in the apical membrane of the same cell; however, the basolateral channels were 2–4 times more densely distributed than the apical counterparts. Also frequently (57%) detected was a Cl − channel of 80.0 ± 0.5 pS ( N = 6), whose activity was Ca 2+ independent. Additionally, this Cl − channel had: 1) linear I-V relations with symmetric Cl −, 2) a permeability sequence of Cl −>Br −>I −≥NO 3 −≥gluconate −, and 3) a complete and reversible block by 1 mM diphenylamine-2-carboxylate. In contrast to the apical Cl − channels, the basolateral ones had a much higher density (57% vs. < 1%) as well as a higher unit conductance (80 pS vs. 50 pS) than the apical counterpart. The relative abundance of these two types as the major conductive pathways for Na +, K +, and Cl − in the basolateral region must be taken into account when addressing the role of strial marginal cells in generating the positive endocochlear potential. The Cl − channel may facilitate Cl − distribution across the basolateral membrane.