4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and indacrinone

We have investigated the volume-activated transport of organic solutes in flounder erythrocytes. Osmotic swelling of cells suspended in a Na(+)-free medium led to increased membrane transport of taurine, glucose, and uridine. For each compound there was a significant lag period (1-2 min at 10 degrees C) between cell swelling and activation of the flux. The volume-activated fluxes of each of the substrates increased in parallel with increasing cell volume, and those of taurine and uridine increased linearly with concentration (up to 19 mM). The volume-activated fluxes of each of the three compounds showed similar sensitivities to a number of anion-selective channel blockers (5-nitro-2-(3-phenylpropylamino)benzoic acid > 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid approximately MK-196 > niflumic acid > furosemide); the IC50 for the inhibition of the volume-activated fluxes by NPPB was around 12 microM. The results are consistent with the hypothesis that the volume-activated transport of organic osmolytes is via a pathway with the characteristics of a volume-activated "chloride channel." This raises the question of whether the transport of organic substrates might represent a physiological role for such channels in other cell types.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Biological Transport; Blood Glucose; Chloride Channels; Diuretics; Erythrocytes; Flounder; Furosemide; Hypotonic Solutions; Indans; Ion Channels; Kinetics; Membrane Proteins; Niflumic Acid; Nitrobenzoates; Taurine; Uridine

Ouabain-insensitive Tl+ uptake by canine iliac arteries was studied. A significant fraction was halide-sensitive, with Br- substituting well for Cl-. The halide-sensitive component was inhibited by diuretics (MK196, bumetanide), PCMBS, low temperatures and external cations K+, Rb+. External but not internal Na+ was necessary for the uptake process. The process was not sensitive to disulphonic stilbenes. The halide-sensitive uptake appears to represent the operation of a (Na+/K+/Cl-)-cotransport process in arteries.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4-Chloromercuribenzenesulfonate; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Bromides; Bumetanide; Chlorides; Dogs; Iliac Artery; Indans; Lithium; Ouabain; Potassium; Rubidium; Temperature; Thallium