Effects of fluoride and vanadate on K+ transport across the erythrocyte membrane of Rana temporaria.
K-Cl cotransport activity in frog erythrocytes was estimated as a Cl- -dependent component of K+ efflux from cells incubated in Cl- - or NO3- -containing medium at 20 degrees C. Decreasing the osmolality of the medium resulted in an increase in K+ efflux from the cells in a Cl- medium but not in an NO3- medium. Treatment of red cells with 5 mM NaF caused a significant decrease (approximately 50%) in K+ loss from the cells in iso- and hypotonic Cl- media but only a small decrease in K+ loss in isotonic NO3- medium. Addition of 1 mM vanadate to an isotonic Cl- medium also led to a significant reduction in K+ efflux. Similar inhibitory effects of NaF and vanadate on K+ efflux in a Cl- medium, but not in an NO3- medium were observed when the incubation temperature was decreased from 20 to 5 degrees C. Thus, under various experimental conditions, NaF and vanadate inhibited about 50% of Cl- -dependent K+ efflux from frog red cells probably due to inhibition of protein phosphatases. Cl- -dependent K+ (86Rb) influx into frog erythrocytes was nearly completely blocked (approximately 94%) by 5 mM NaF. In a NO3- medium, K+ influx was mainly mediated by the Na+,K+ pump and was unchanged in the presence of 5 mM NaF, 0.03 mM Al3+ or their combination. These data indicate that G proteins or cAMP are not involved in the regulation of Na+,K+ pump activity which is activated by catecholamines and phosphodiesterase blockers in these cells.
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg.
N I
NI
Agalakova
A V
AV
Lapin
G P
GP
Gusev
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D003080:Cold Temperature / Q000009:adverse effects; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005459:Fluorides / Q000494:pharmacology*; D007038:Hypotonic Solutions / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011896:Rana temporaria / Q000033:anatomy & histology / Q000378:metabolism*; D012414:Rubidium Radioisotopes; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects* / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology*
D007038:Hypotonic Solutions; D007552:Isotonic Solutions; D012414:Rubidium Radioisotopes; D014638:Vanadates; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005459:Fluorides; D011188:Potassium