Characterization of a Na(+)-K(+)-2Cl- cotransport system in oocytes from Xenopus laevis.
In order to characterize the transport systems mediating K+ uptake into oocytes, flux studies employing 86Rb were performed on Xenopus oocytes stripped of follicular cells by pretreatment with Ca2(+)-Mg2(+)-free Barth's medium. Total Rb+ uptake consisted of an ouabain-sensitive and an ouabain-insensitive flux. In the presence of 100 mmol/l NaCl and 0.1 mmol/l ouabain the ouabain-insensitive flux amounted to 754.7 +/- 59.9 pmol/oocyte per h (n = 30 cells, i.e., 10 cells each from three different animals). In the absence of Na+ (Na+ substituted by N-methylglucamine) or when Cl- was replaced by NO3- the ouabain-insensitive flux was reduced to 84.4 +/- 42.9 and 79.2 +/- 12.1 pmol/oocyte per h, respectively (n = 50 cells). Furthermore, this Na(+)- and Cl(-)-dependent flux was completely inhibited by 10(-4) mol/l bumetanide, a specific inhibitor of the Na(+)-K(+)-2Cl- cotransport system. These results suggest that K+ uptake via a bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport system represents a major K+ pathway in oocytes.
Shetlar
R E
RE
Max-Planck-Institut für Systemphysiologie, Dortmund, F.R.G.
Schölermann
B
B
Morrison
A I
AI
Kinne
R K
RK
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008536:Meglumine / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D012414:Rubidium Radioisotopes / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014982:Xenopus laevis
D002352:Carrier Proteins; D002712:Chlorides; D009566:Nitrates; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D008536:Meglumine; C031618:sodium nitrate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium