title: Membrane potentials and intracellular chloride activity in the ciliary body of the shark.
abstract: We have found that membrane potential in the isolated ciliary epithelium of the shark, Squalus acanthias, is -53 mV. High extracellular potassium or ouabain (10(-5) mol X l-1) decrease the potential, and furosemide (10(-4) mol X l-1) hyperpolarizes it. There is no difference in membrane potential between the cells of the non-pigmented and pigmented layers. Intracellular chloride activity (64 mmol X l-1) was significantly higher than could be predicted from the equilibrium distribution (26 mmol X l-1) across the cell membranes. When furosemide was applied to the aqueous side of the epithelium, intracellular chloride activity decreased to 35 mmol X l-1 and approached electrochemical equilibrium. The data indicate that the ciliary epithelium possesses an active, furosemide-sensitive chloride transport mechanism which could be a Na-Cl or a 1 Na-1 K-2 Cl symport.
mesh_terms: D000818:Animals; D002712:Chlorides / Q000502:physiology*; D002924:Ciliary Body / Q000502:physiology*; D004284:Dogfish / Q000502:physiology*; D004848:Epithelium / Q000502:physiology; D005665:Furosemide / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D012754:Sharks / Q000502:physiology*
chemical_list: D002712:Chlorides; D010042:Ouabain; D005665:Furosemide