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

The K+ secretory epithelium of the vestibular labyrinth (dark cells) was impaled with glass microelectrodes in order to test the hypothesis that it contains a large Cl- conductance. In the first series of experiments, the short-circuited epithelium was perfused on both sides by a solution containing 150 mmol/l Cl-. The membrane voltage (PD) was -18 +/- 1 mV (N = 101), showed a Gaussian distribution, and the estimated input resistance of the cell (R 'cell') was 17 +/- 3 M omega. The PD responded to 10(-4) mol/l ouabain with a depolarization, suggesting the presence of a (Na(+) + K+)-ATPase. The PD responses to Cl- steps yielded an apparent transference number tCl = 0.34 +/- 0.03 (N = 65) and those to K+ steps yielded a tK = 0.16 +/- 0.01 (N = 48). In the second series of experiments, cells presumed to be Cl(-)-depleted were impaled in Cl(-)-free solutions. The distribution of the PD was not Gaussian; PDs as negative as -90 mV were observed. Cells with a highly negative PD also had a high R 'cell'. With the addition of Cl- the PD collapsed to -19 +/- 1 mV and R collapsed to 16 +/- 3 M omega (N = 145) which are not significantly different from values obtained in the first series of experiments when cells were impaled in a solution containing 150 mmol/l Cl-. Alternating the bath perfusate between Cl(-)-free and Cl(-)-containing solutions led to large PD transients.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Animals; Chloride Channels; Chlorides; Diphenylamine; Diuretics; Electrodes, Implanted; Epithelium; Gerbillinae; Membrane Potentials; Membrane Proteins; Nitrobenzoates; Ouabain; Potassium; Sodium-Potassium-Exchanging ATPase; Sulfonamides; Vestibule, Labyrinth

Excitatory postsynaptic potentials (termed U1 and U2) were extracellularly recorded from the frog optic tectum in vitro following electrical stimulation of the contralateral optic nerve. Gamma-Aminobutyric acid (GABA) and glycine elicited a large and sustained enhancement of these synaptic waves. In the presence of the Cl- transport inhibitor ammonium (NH+4) the effects of GABA or glycine were progressively reduced to about 50% of their initial action without changes in the control synaptic waves. In 50% Cl- media the depression of GABA and glycine responses by NH+4 was more intense. Other Cl- transport inhibitors such as bumetanide, piretanide and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonate (SITS) were inactive against responses to GABA or glycine. Penicillin, a Cl- channel blocker, antagonized the action of GABA and glycine, while increasing the amplitude of the U2 waveform. The present results provide pharmacological evidence in support of the Cl- dependence of the unusual action of GABA or glycine in facilitating excitatory synaptic transmission in the optic tectum.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Ammonium Chloride; Animals; Bumetanide; Diuretics; Electric Stimulation; GABA Antagonists; gamma-Aminobutyric Acid; Glycine; Kinetics; Optic Nerve; Penicillins; Rana temporaria; Receptors, GABA-A; Sulfonamides; Superior Colliculi

Passive (ouabain-insensitive) Na+ and K+ effluxes from human red blood cells were measured over the range pHo 6.2-8.5. On raising pHo, Na+ efflux increased and this was mainly attributable to the piretanide-sensitive component: K+ efflux likewise but attributable to both piretanide-sensitive and piretanide-insensitive components. On replacing Cl- with non-penetrating anions (mainly gluconate), Na+ and K+ effluxes increased, mostly attributable to the piretanide-insensitive components. On restoring pHi either by reducing pHo or by applying DIDS, the influence of pHo on Na+ and K+ effluxes was diminished. These results suggest that pHi rather than Em is the dominant influence. Passive Na+ and K+ effluxes and influxes in the presence of bumetanide were tested fro conformity to the Ussing independence relationship. For K+, the calculated and observed ratios agreed, indicating that the sodium pump, 'cotransport' and leak wholly account for K+ fluxes in human red blood cells. For Na+, the ratios did not agree and a 1:1 Na+/Na+ exchange did not account for the discrepancy. Pathways for Na+ appear to be more numerous than for K+.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adult; Anions; Bumetanide; Erythrocytes; Humans; Hydrogen-Ion Concentration; Mathematics; Membrane Potentials; Ouabain; Potassium; Sodium; Sodium-Potassium-Exchanging ATPase; Sulfonamides