gramicidin-a and 1-9-dideoxyforskolin

Exposure of NIH/3T3 fibroblasts not expressing P-glycoprotein to 50, 30, 20, and 10% hyposmotic solutions led to cell volume increases of 70, 32, 21, and 12%, respectively. After swelling, NIH/3T3 cells exhibited regulatory volume decrease (RVD), attaining complete volume recovery after 30 min except in 50% hyposmotic solution, in which volume recovery was 76%. RVD was accelerated by gramicidin and inhibited by the Cl channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoic acid, 1,9-dideoxyforskolin, dipyridamole, and niflumic acid and by the K channel, blocker quinidine. RVD was reduced 15% by removal of extracellular Ca. The pathway opened by hypotonicity was highly permeable to K and Rb and only partly permeable to other cations. Most anions were able to permeate, with a permeability ranking of nitrate > benzoate = iodide > thiocyanate > chloride > > gluconate. The pathway was permeable to neutral amino acids, with a permeability ranking of glycine > alanine > glutamate > taurine > gamma-aminobutyric acid > glutamine. The pathway was not permeable to basic amino acids. These results show that, despite the absence of P-glycoprotein, NIH/3T3 cells exhibit RVD with properties similar to those expressed in most cell types.

Topics: 3T3 Cells; 4-Aminopyridine; Animals; Anions; ATP Binding Cassette Transporter, Subfamily B, Member 1; Barium; Cell Membrane Permeability; Chloride Channels; Chlorides; Colchicine; Colforsin; Dipyridamole; Gramicidin; Kinetics; Mice; Niflumic Acid; Nitrobenzoates; Potassium Channel Blockers; Potassium Channels; Quinidine; Tetraethylammonium; Tetraethylammonium Compounds; Time Factors; Water-Electrolyte Balance