Dual role of ATP in supporting volume-regulated chloride channels in mouse fibroblasts.

The effects of inhibitors of protein tyrosine kinases (PTKs) on the Cl(-) current (I(Cl(vol))) through volume-regulated anion/chloride (VRAC) channels whilst manipulating cellular ATP have been studied in mouse fibroblasts using the whole-cell patch clamp technique. Removal of ATP from the pipette-filling solution prevented activation of the current during osmotic cell swelling and when the volume of patched cells was increased by the application of positive pressure through the patch pipette to achieve rates exceeding 100%/min. Equimolar substitution of ATP in the pipette solution with its non-hydrolyzable analogs, adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS) or adenylyl-(beta,gamma-methylene)-diphosphonate (AMP-PCP), not only supported activation of the current but also maintained its amplitude.

Hypotonic cell swelling induces translocation of the alpha isoform of cytosolic phospholipase A2 but not the gamma isoform in Ehrlich ascites tumor cells.

We demonstrate that two isoforms of the cytosolic phospholipase A2, cPLA2alpha and cPLA2gamma, are present in Ehrlich ascites tumor cells. Both enzymes are almost uniformly distributed throughout the cells under control conditions, as visualized by laser-scanning confocal microscopy. Stimulation by either hypotonic cell swelling or addition of the Ca2+ ionophore A23187 results in translocation of cPLA2alpha, but not cPLA2gamma, to the nucleus, where it forms hot-spot-like clusters.

Protein phosphotyrosine phosphatase inhibitors suppress regulatory volume decrease and the volume-sensitive Cl- conductance in mouse fibroblasts.

The effects of the protein tyrosine phosphatase (PTP) inhibitors, pervanadate, monoperoxo(picolinato)- oxo-vanadate(V) [mpV(pic)] and dephostatin, on regulatory volume decrease (RVD) and the volume-sensitive Cl- current in mouse L-fibroblasts were studied with the aid of video microscopy and the whole-cell patch-clamp technique. The RVD induced by the hyposmotic shift from 300 to 150 mosmol/l, was strongly suppressed in cells that had been pre-incubated in pervanadate (25 microM) or in mpV(pic) (10 microM), or subjected to extracellular application of dephostatin (20 microM). The acceleration in RVD caused by gramicidin (0.

Cell swelling activates phospholipase A2 in Ehrlich ascites tumor cells.

Ehrlich ascites tumor cells, loaded with 3H-labeled arachidonic acid and 14C-labeled stearic acid for two hours, were washed and transferred to either isotonic or hypotonic media containing BSA to scavenge the labeled fatty acids released from the cells. During the first two minutes of hypo-osmotic exposure the rate of 3H-labeled arachidonic acid release is 3.3 times higher than that observed at normal osmolality.

The osmolality-sensitive taurine channel in flounder erythrocytes is strongly stimulated by noradrenaline under hypo-osmotic conditions.

Stimulation of flounder erythrocytes by noradrenaline under isosmotic conditions (330 mosmol kg-1) and physiological Na+ concentration (113 mmol l-1) caused swelling of the cells. The EC50 of this cell swelling was 0.65 µmol l-1 noradrenaline.