Cardiac glycosides inhibit the sodium pump. However, some studies suggest that nanomolar ouabain concentrations can stimulate the activity of the sodium pump. In this study, using the Na þ /K þ -ATPase of human erythrocytes, we compared the effect of digoxin, ouabain and an ouabain like-factor (OLF), on 86Rb uptake. Ouabain concentrations below 10 9M significantly stimulate Rb þ uptake, and the maximal increase above base-line values is 185% at 10 10M ouabain. No stimulation is observed in the same conditions by digoxin. OLF behaved like ouabain, producing an activation of Rb þ flux at concentrations lower than 10 9Mouabain equivalents (143% at 10 10 M). Western blot analysis revealed the presence of both a1 and a3 pump isoforms in human erythrocytes. Our data confirm the analogies between OLF and ouabain and suggest that Na þ /K þ -ATPase activation may be related to the a3 isoform. In addition, we investigated whether ouabain at different concentrations was effective in altering the intracellular calcium concentration of erythrocytes. We found that ouabain at concentration lower than 10 9M did not affect this homeostasis.
Erythrocyte sodium pump stimulation by ouabain and an endogenous ouabain-like factor
PELLEGRINO, MARIO;MONTALI, UMBERTO
2007-01-01
Abstract
Cardiac glycosides inhibit the sodium pump. However, some studies suggest that nanomolar ouabain concentrations can stimulate the activity of the sodium pump. In this study, using the Na þ /K þ -ATPase of human erythrocytes, we compared the effect of digoxin, ouabain and an ouabain like-factor (OLF), on 86Rb uptake. Ouabain concentrations below 10 9M significantly stimulate Rb þ uptake, and the maximal increase above base-line values is 185% at 10 10M ouabain. No stimulation is observed in the same conditions by digoxin. OLF behaved like ouabain, producing an activation of Rb þ flux at concentrations lower than 10 9Mouabain equivalents (143% at 10 10 M). Western blot analysis revealed the presence of both a1 and a3 pump isoforms in human erythrocytes. Our data confirm the analogies between OLF and ouabain and suggest that Na þ /K þ -ATPase activation may be related to the a3 isoform. In addition, we investigated whether ouabain at different concentrations was effective in altering the intracellular calcium concentration of erythrocytes. We found that ouabain at concentration lower than 10 9M did not affect this homeostasis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
