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Journal of Experimental Biology, Vol 191, Issue 1 89-105, Copyright © 1994 by Company of Biologists

JOURNAL ARTICLES

ACTIVATION AND PHYSIOLOGICAL ROLE OF Na+/H+ EXCHANGE IN LAMPREY (LAMPETRA FLUVIATILIS) ERYTHROCYTES

L Virkki and M Nikinmaa

The effects of intracellular acidification, osmotic shrinkage and ß-adrenergic stimulation on sodium transport across the membrane of lamprey (Lampetra fluviatilis) erythrocytes were investigated. Unidirectional ouabain-insensitive sodium flux, measured using radioactive 22Na, was increased markedly by intracellular acidification, to a lesser extent by osmotic shrinkage and only modestly by ß-adrenergic stimulation. Na+/H+ exchange was activated in all of these cases. However, net sodium influx (and cell swelling caused by the influx of osmotically obliged water) was seen only in cells subjected to intracellular acidification. In contrast, practically no changes in red cell pH or in water or ion (Na+, K+ and Cl-) contents were seen after osmotic shrinkage or ß-adrenergic stimulation. Calculations of the [Na+]o/[Na+]i and [H+]o/[H+]i ratios across the erythrocyte membrane suggest that the virtual lack of net sodium movements in osmotically shrunken erythrocytes is due to the absence of a driving force for net transport of these ions via the Na+/H+ exchange pathway. It also appears that, in physiological conditions, the increase in the activity of the Na+/H+ exchanger by ß-adrenergic stimulation is too small to mediate detectable net sodium transport.


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Y. Weaver, K Kiessling, and A. Cossins
Responses of the Na+/H+ exchanger of european flounder red blood cells to hypertonic, &bgr;-adrenergic and acidotic stimuli
J. Exp. Biol., January 1, 1999; 202(1): 21 - 32.
[Abstract] [PDF]


© The Company of Biologists Ltd 1994