[23Na-NMR measurements of the sodium concentration in guinea pig erythrocytes: the effects of cardiac glycoside and asebotoxin III].
Intra- and extracellular sodium in guinea pig erythrocytes was evaluated with sodium-23 nuclear magnetic resonance (23Na-NMR) by the use of a shift reagent, Dy(TTHA)3- or Dy(PPPi)2(7-). The test medium contained erythrocytes at 40% hematocrit level and NMR buffer (145 mM NaCl, 10 mM Dy(TTHA)3-, 10% D2O, adjusted to pH 7.4 with tris, at 35 degrees C). NMR spectra were obtained with a JEOL GSX 400 spectrometer operating at the Fourier transform mode of resonance signals, and the accumulated signals provoked by radio-frequency pulses of 90 degrees were recorded on paper. Quantitative Na determination was performed by measuring the area under the peak of intracellular sodium (Nai) NMR signals. Ouabain (Oua: 0.3 mM) and asebotoxin-III (ATX-III: 0.3 mM) produced an increase in Nai-NMR signals to a level of 188.1% and 138.1% of the control, respectively. Combined use of Oua (0.15 mM) and ATX-III (0.15 mM) produced an elevation of Nai concentration to a high level of 219.0% of the control in a superadditive manner. Mechanisms of the Nai elevation with Oua and ATX-III can be interpreted by assuming two different actions: ATX-III increases net Na(+)-influx via Na+ channels, while Oua inhibits the pumping out of Na+ from the cell.
Hotta
Y
Y
Department of Pharmacology, Aichi Medical University, Japan.
Ando
H
H
Eto
R
R
Takeya
K
K
Haruna
M
M
Ito
K
K
Sakakibara
J
J
D000818:Animals; D004357:Drug Synergism; D004912:Erythrocytes / Q000378:metabolism*; D006168:Guinea Pigs; D009682:Magnetic Resonance Spectroscopy; D010042:Ouabain / Q000494:pharmacology*; D012964:Sodium / Q000097:blood* / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology*
D015222:Sodium Channels; D013729:Terpenes; C024877:asebotoxin III; D010042:Ouabain; D012964:Sodium