Effects of phorbol 12-myristate 13-acetate on potassium transport in the red blood cells of frog Rana temporaria.
Phorbol 12-myristate 13-acetate (PMA), a stimulator of PKC, was examined for its influence on K(+) ((86)Rb) influx in the frog erythrocyte. PMA, 0.1 microM, was found to accelerate ouabain-sensitive K(+) influx, which was suppressed by 73% with 1 mM amiloride, indicating secondary activation of the Na(+)-K(+)-pump due to stimulation of Na(+ )/H(+) exchange. PMA-induced stimulation of the sodium pump was completely inhibited with 1 microM staurosporine and by approximately 50% with 20 microM chelerythrine. In contrast to Na(+)-K(+)-pump, an activity of Cl(-)-dependent K(+) transport (K-Cl cotransport, KCC), calculated as the difference between K(+) influxes in Cl(-) and NO(3) (-)-media, was substantially decreased under the influence of PMA. Staurosporine fully restored the PMA-induced inhibition of KCC, whereas chelerythrine did not exert any influence. Osmotic swelling of the frog erythrocytes was accompanied by approximately twofold stimulation of KCC. Swelling-activated KCC was inhibited by approximately 50 and approximately 83% in the presence of PMA and genistein, respectively, but not chelerythrine. Exposure of the frog erythrocytes to 5 mM fluoride (F(-)) also reduced the KCC activity in isotonic and hypotonic media, with maximal suppression of K(+) influx in both media being observed upon simultaneous addition of PMA and F(-). Furosemide and [(dihydronindenyl)oxy] alkanoic acid inhibited the K(+) influx in both the media by approximately 50-60%. The results obtained show both the direct and indirect effects of PMA on the K(+) transport in frog erythrocytes and a complicated picture of KCC regulation in frog erythrocytes with involvement of PKC, tyrosine kinase and protein phosphatase.
Agalakova
Natalia Ivanovna
NI
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg, Russia. agalak@iephb.ru
Gusev
G P
GP
D000818:Animals; D004912:Erythrocytes / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011896:Rana temporaria / Q000378:metabolism*; D012414:Rubidium Radioisotopes; D012588:Scintillation Counting; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D027981:Symporters / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives* / Q000494:pharmacology
D012414:Rubidium Radioisotopes; D027981:Symporters; C016658:phorbolol myristate acetate; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium