Potassium transport in red blood cells of frog Rana temporaria: demonstration of a K-Cl cotransport.
Pathways of K+ movement across the erythrocyte membrane of frog Rana temporaria were studied using 86Rb as a tracer. The K+ influx was significantly blocked by 0.1 mmol.l-1 ouabain (by 30%) and 1 mmol.l-1 furosemide (by 56%) in the red cells incubated in saline at physiological K+ concentration (2.7 mmol.l-1). Ouabain and furosemide had an additive effect on K+ transport in frog red cells. The ouabain-sensitive and furosemide-sensitive components of K+ influx saturated as f(K+)e with apparent Km values for external Ke+ concentration of 0.96 +/- 0.11 and 4.6 +/- 0.5 mmol.l-1 and Vmax of 0.89 +/- 0.04 and 2.8 +/- 0.4 mmol.l cells-1.h-1, respectively. The residual ouabain-furosemide-resistant component was also a saturable function of Ke+ medium concentration. Total K+ influx was significantly reduced when frog erythrocytes were incubated in NO3- medium. Furosemide did not affect K+ transport in frog red cells in NO3- media. At the same Ke+ concentration the ouabain-furosemide-insensitive K+ influx in Cl- medium was significantly greater than that in NO3- medium. We found no inhibitory effect of 1 mmol.l-1 furosemide on Na+ influx in frog red cells in Cl- medium. K+ loss from the frog erythrocytes in a K(+)-free medium was significantly reduced (mean 58%) after replacement of Cl- with NO3-. Furosemide (0.5 mmol.l-1) did not produce any significant reduction in the K+ loss in both media. The Cl(-)-dependent component of K+ loss from frog red cells was 5.7 +/- 1.2 mmol.l-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Gusev
G P
GP
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg.
Agalakova
N I
NI
Lapin
A V
AV
D000818:Animals; D002352:Carrier Proteins / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011896:Rana temporaria / Q000097:blood*; D012964:Sodium / Q000378:metabolism; D027981:Symporters; D013997:Time Factors; D000096922:K Cl- Cotransporters
D002352:Carrier Proteins; D002712:Chlorides; D005665:Furosemide; D009566:Nitrates; D010042:Ouabain; D011188:Potassium; D012964:Sodium; D027981:Symporters; D000096922:K Cl- Cotransporters