Inhibition and stimulation of K+ transport across the frog erythrocyte membrane by furosemide, DIOA, DIDS and quinine.
Frog erythrocytes were incubated in iso- or hypotonic media containing 10 mmol/l Rb+ and 0.1 mmol/l ouabain and both Rb+ uptake and K+ loss were measured simultaneously. Rb+ uptake by frog red cells in iso- and hypotonic media was reduced by 30-60% in the presence of 0.01-0.1 mmol/l [(dihydroindenyl)oxy] alkanoic acid (DIOA) or 0.5-1.0 mmol/l furosemide. Furosemide inhibited K+ loss from frog erythrocytes incubated in hypotonic media but did not affect it in isotonic media. DIOA at a concentration of 0.05 mmol/l inhibited of K+ loss from frog erythrocytes in both iso- and hypotonic media. At the concentrations of 0.01 and 0.02 mmol/l DIOA significantly suppressed K+ loss in a K+-free chloride medium but not in a K+-free nitrate medium. The Cl(-)-dependent K+ loss was completely blocked at a concentration of 0.1 mmol/l DIOA and the concentration required for 50% inhibition of K-Cl cotransport was approximately 0.015 mmol/l. However, the inhibitory effect of DIOA on K-Cl cotransport was masked by an opposite stimulatory effect on K+ transport which was also observed in nitrate medium. Quinine in a concentration of 0.2-1.0 mmol/l was able to inhibit Rb+ uptake and K+ loss only in hypotonic media. In isotonic media, quinine produced a stimulation of Rb+ uptake and K+ loss. A three to five-fold activation of Rb+ uptake and K+ loss was consistently observed in frog erythrocytes treated with 0.05-0.2 mmol/l 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). In contrast, another stilbene derivative 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS) had no effect on K+ transport in the cells. Thus, of these drugs tested in the present study only DIOA at low concentrations may be considered as a selective blocker of the K-Cl cotransporter in the frog red blood cells.
Gusev
G P
GP
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg. gusev@ief.spb.su
Lapin
A V
AV
Agalakova
N I
NI
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002264:Carboxylic Acids / Q000494:pharmacology*; D002712:Chlorides / Q000097:blood; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000502:physiology*; D005665:Furosemide / Q000494:pharmacology*; D007192:Indenes / Q000494:pharmacology*; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D011803:Quinine / Q000494:pharmacology*; D011896:Rana temporaria; D012413:Rubidium / Q000493:pharmacokinetics
C059990:((dihydroindenyl)oxy)alkanoic acid; D002264:Carboxylic Acids; D002712:Chlorides; D007192:Indenes; D010042:Ouabain; D005665:Furosemide; D011803:Quinine; D012413:Rubidium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium