1887

Abstract

The primitive free-living protozoon was found to maintain a cell volume of approximately 260 fl under standard culture conditions. On increasing the extracellular osmolality the volume decreased and the cells remained shrunken for >30 min. By contrast, a decrease in the external osmolality resulted in a transient increase in cell volume which was followed by an efficient ‘regulatory volume decrease’ (RVD). contains high concentrations of amino acids, with alanine constituting over 70% of the total amino acid pool. Exposure to hypo-osmotic medium resulted in the loss from the cell of both amino acids and K, via one or more swelling-activated pathways. The efflux of amino acids and K, together with a charge-balancing counter-anion, accounted almost fully for the observed RVD. The pharmacological properties of the swelling-activated pathways differ from those of volume-sensitive transporters and channels described previously in other cell types.

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2000-02-01
2020-01-26
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