Ionic mechanism of ouabain-induced swelling of leech Retzius neurons

Abstract

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.

Activity-dependent suppression of spontaneous spike generation in the Retzius neurons of the leech Hirudo medicinalis L.

“…In an initial phase of this study we have used ouabain to block the Na/K pump. However, as has been shown before (Hochstrate and Schlue 2001;Dierkes et al 2006) and also in our experiments, ouabain has a marked depolarizing effect on Rz neurons and completely abolishes spiking activity. In our hands, even concentrations in the low micromolar range fully blocked spontaneous and evoked spiking which prevented the use of this agent in our study.…”

Computation of Pump-Leak Flux Balance in Animal Cells

“…Nevertheless, real cells following pump inhibition by ouabain often do not swell for a long time. Low permeability of Cl - channels as well as the involvement of the Ca-ATPase pump, Na-Ca antiporter and NKCC cotransport have been listed as possible reasons for the delay in swelling [19,20,21]. Fig.…”

Na+/K+-pump and neurotransmitter membrane receptors

“…The mechanism underlying ouabain-induced swelling of the leech, H. medicinalis , Retzius cells have been investigated using triple-barrelled ion-sensitive electrodes (Dierkes et al 2006). Ouabain (500 µM) increased intracellular Na + concentration, decreased intracellular K + concentration, increased intracellular Cl − concentration and depolarized the MP.…”