Effect of hypoxia on Na(+)-K(+)-Cl- cotransport in cultured brain capillary endothelial cells of the rat.
The effect of hypoxia on Na+, K(+)-ATPase and Na(+)-K(+)-Cl- cotransport activity in cultured rat brain capillary endothelial cells (RBECs) was investigated by measuring 86Rb+ uptake as a tracer for K+. RBECs expressed both Na+, K(+)-ATPase and Na(+)-K(+)-Cl- cotransport activity (4.6 and 5.5 nmol/mg of protein/min, respectively). Hypoxia (24 h) decreased cellular ATP content by 43.5% and reduced Na+, K(+)-ATPase activity by 38.9%, whereas it significantly increased Na(+)-K(+)-Cl- cotransport activity by 49.1% in RBECs. To clarify further the mechanism responsible for these observations, the effect of oligomycin-induced ATP depletion on these ion transport systems was examined. Exposure of RBECs to oligomycin led to a time-dependent decrease of cellular ATP content (by approximately 65%) along with a complete inhibition of Na+, K(+)-ATPase and a coordinated increase of Na(+)-K(+)-Cl- cotransport activity (up to 100% above control values). Oligomycin augmentation of Na(+)-K(+)-Cl- cotransport activity was not observed in the presence of 2-deoxy-D-glucose (a competitive inhibitor of glucose transport and glycolysis) or in the absence of glucose. These results strongly suggest that under hypoxic conditions when Na+, K(+)-ATPase activity is reduced, RBECs have the ability to increase K+ uptake through Na(+)-K(+)-Cl-cotransport.
Kawai
N
N
Stroke Branch, NINDS, NIH, Bethesda, Maryland 20892-4128, USA.
McCarron
R M
RM
Spatz
M
M
D000255:Adenosine Triphosphate / Q000172:deficiency; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002021:Buffers; D002196:Capillaries / Q000166:cytology / Q000378:metabolism*; D002352:Carrier Proteins / Q000187:drug effects / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured / Q000378:metabolism; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D003847:Deoxyglucose / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D005947:Glucose / Q000172:deficiency; D009840:Oligomycins / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000502:physiology; D014475:Uncoupling Agents / Q000494:pharmacology
D000963:Antimetabolites; D002021:Buffers; D002352:Carrier Proteins; D018118:Chloride Channels; D009840:Oligomycins; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D014475:Uncoupling Agents; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; D011188:Potassium