KCl cotransport activation in human erythrocytes by high hydrostatic pressure.
1. Pressure induced a 4- to 5-fold stimulation of the residual (i.e. oubain-bumetanide insensitive) 86Rb+ influx across the human red cell membrane. This enhancement showed a broad pHo dependence with a maximum stimulation around pHo 7. 2. At atmospheric pressure, the protein kinase inhibitors staurosporine and chelerythrine stimulated a normally silent component of 86Rb+ influx in a dose-dependent manner with a half-maximum stimulatory concentration at about 550 nM and 140 microM, respectively. The component stimulated by staurosporine was entirely Cl- dependent, but part of the chelerythrine effect was Cl- independent. 3. Staurosporine (3 microM), chelerythrine (200 microM) and N-ethylmaleimide (1 mM) stimulated further the increased residual 86Rb+ influx in cells at high pressure. 4. The serine/threonine protein phosphatase inhibitors okadaic acid, cantharidin and calyculin A inhibited the stimulatory pressure effect in a dose-dependent manner with half-maximum inhibitory concentrations of 70 nM, 2.5 microM and 3.3 nM, respectively. In contrast, deltamethrin, a specific protein phosphatase type 2B inhibitor, did not affect the stimulation by pressure, up to a concentration of 10 microM. 5. Decreasing the internal ionized magnesium concentration ([Mg2+]i) with A23187 and EDTA stimulated the increased residual 86Rb+ influx in cells at high pressure. On the other hand, increasing the [Mg2+]i nearly abolished the stimulatory pressure effect. 6. Decreasing the [Mg2+]i produced a marked change in the pHo dependence curve, with a linear increase of the 86Rb+ influx at higher pHo values. 7. We demonstrate that high pressure stimulates the normally silent component of 86Rb+ influx by modifying the phosphorylation/dephosphorylation ratio of the KCl cotransporter.
Godart
H
H
University Laboratory of Physiology, Oxford, UK.
Ellory
J C
JC
D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011189:Potassium Chloride / Q000378:metabolism*; D011312:Pressure; D012413:Rubidium / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D011189:Potassium Chloride; D019311:Staurosporine; D012413:Rubidium