Pervanadate inhibits volume-sensitive chloride current in bovine chromaffin cells.
The role of protein tyrosine phosphorylation in the activation of the volume-sensitive Cl- current in bovine chromaffin cells was investigated by studying the effects of inhibitors of protein tyrosine kinases (PTKs) and phosphatases (PTPs). The whole-cell current was induced by intracellular guanosine-5'-0-(3-thiotriphosphate) (GTP-[gamma-S], 100-250 microM), the nonhydrolysable GTP analogue, or by cell inflation through the patch pipette under voltage-clamp conditions. PTK inhibitors tyrphostin B46 (5-50 microM) and genistein (200 microM) did not inhibit the volume-sensitive Cl- current nor did they induce it in the absence of other stimuli. In contrast, the PTP inhibitor pervanadate (200 microM) applied intracellularly prevented activation of the current. Voltage-activated Na+ and Ca2+ currents were unaffected by pervanadate. Neither sodium orthovanadate nor hydrogen peroxide alone mimicked the action of pervanadate. Other PTP inhibitors tested, i.e. ammonium molybdate (10-100 microM), phenylarsine oxide (10 microM), and ZnCl2 (500 microM), as well as the serine/threonine protein phosphatases inhibitor okadaic acid (200 nM) failed to inhibit the volume-sensitive Cl- current. It is suggested that the inhibitory action of pervanadate indicates the involvement of protein tyrosine phosphorylation in the regulation of volume-sensitive Cl- channels in bovine chromaffin cells. The possibility of pervanadate acting via a pathway unrelated to protein phosphorylation is also discussed.
Doroshenko
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Loeb Research Institute, 1053 Carling Avenue, Ottawa, Ontario, K1Y 4E9, Canada.
D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects* / Q000502:physiology*; D002838:Chromaffin System / Q000502:physiology*; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D020032:Tyrphostins; D014638:Vanadates / Q000494:pharmacology*
D001597:Benzylidene Compounds; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D009570:Nitriles; D020032:Tyrphostins; C095713:alpha-cyano-(3,4-dihydroxy)-N-(3-phenylpropyl)cinnamide; C076715:pervanadate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D014638:Vanadates; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017027:Protein Tyrosine Phosphatases