Ionic mechanism of ouabain-induced swelling of leech Retzius neurons.
By using electrophysiological and microfluorimetric methods, we found that leech Retzius neurons swell after inhibition of the Na(+)-K(+) pump by the cardiac glycoside ouabain. To explore the mechanism of this swelling, we measured the effect of ouabain on [Na(+)](i), [K(+)](i), and [Cl(-)](i), as well as on the membrane potential, by applying triple-barrelled ion-sensitive microelectrodes. As shown previously, ouabain induced a marked [Na(+)](i) increase, a [K(+)](i) decrease, and a membrane depolarization, and it also evoked an increase in [Cl(-)](i). The analysis of the data revealed a net uptake of NaCl, which quantitatively explained the ouabain-induced cell swelling. In the absence of extracellular Na(+) or Cl(-), NaCl uptake was excluded, and the cell volume remained unaffected. Likewise, NaCl uptake and, hence, cell swelling did not occur when the Na(+)-K(+) pump was inhibited by omitting bath K(+). Also, in K(+)-free solution, [Na(+)](i) increased and [K(+)](i) dropped, but [Cl(-)](i) slightly decreased, and after an initial, small membrane depolarization, the cells hyperpolarized for a prolonged period. It is concluded that the ouabain-induced NaCl uptake is caused by the depolarization of the plasma membrane, which augments the inwardly directed electrochemical Cl(-) gradient.
Dierkes
Paul Wilhelm
PW
Institut für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany. dierkes@uni-duesseldorf.de
Wüsten
Hans Joachim
HJ
Klees
Guido
G
Müller
Anja
A
Hochstrate
Peter
P
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016257:Fura-2; D047709:Hirudo medicinalis; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D002712:Chlorides; D004791:Enzyme Inhibitors; D012965:Sodium Chloride; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium; D016257:Fura-2