Nematocytes, the stinging cells of the primitive marine animals jellyfish and sea anemones respond with regulatory volume decrease (RVD) to osmotic swelling in 35% diluted artificial sea water (65% ASW, Marino et al., Cell Physiol Biochem 2010). Since RVD is attained through K+ and Cl- efflux via channels and cotransporters, an active pump mechanism must be required to maintain the cellular K+ gradient and expel Na, which was here explored. Cells were isolated from acontia of the anemone Aiptasia mutabilis (Strait of Messina, Italy) by applying 605mM NaSCN plus 0.01mM Ca2+ and then exposed to isosmotic or 65% hyposmotic ASW in the presence and absence of ouabain, the specific Na/K pump inhibitor. Ouabain present at 10-4 M, but not at 10-6 and 10-8M, induced significant cell swelling in isosmotic ASW suggesting Na/K pump inhibition and failure to extrude Na causing an osmotic influx of water. This effect was attenuated by replacing Na with choline in the ASW. Ouabain applied at 10-4M prior to 65% ASW did not affect the initial osmotic swelling phase but inhibited RVD consistent with loss of K required for this process. Results suggest that nematocytes possess Na/K pumps with low ouabain affinity that actively extrude Na and maintain cellular K steady state levels, necessary to perform RVD.

Evidence for a Na/K pump in nematocytes isolated from sea anemones.

MORABITO, Rossana;MARINO, Angela;LA SPADA, Giuseppa;
2012

Abstract

Nematocytes, the stinging cells of the primitive marine animals jellyfish and sea anemones respond with regulatory volume decrease (RVD) to osmotic swelling in 35% diluted artificial sea water (65% ASW, Marino et al., Cell Physiol Biochem 2010). Since RVD is attained through K+ and Cl- efflux via channels and cotransporters, an active pump mechanism must be required to maintain the cellular K+ gradient and expel Na, which was here explored. Cells were isolated from acontia of the anemone Aiptasia mutabilis (Strait of Messina, Italy) by applying 605mM NaSCN plus 0.01mM Ca2+ and then exposed to isosmotic or 65% hyposmotic ASW in the presence and absence of ouabain, the specific Na/K pump inhibitor. Ouabain present at 10-4 M, but not at 10-6 and 10-8M, induced significant cell swelling in isosmotic ASW suggesting Na/K pump inhibition and failure to extrude Na causing an osmotic influx of water. This effect was attenuated by replacing Na with choline in the ASW. Ouabain applied at 10-4M prior to 65% ASW did not affect the initial osmotic swelling phase but inhibited RVD consistent with loss of K required for this process. Results suggest that nematocytes possess Na/K pumps with low ouabain affinity that actively extrude Na and maintain cellular K steady state levels, necessary to perform RVD.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11570/1954288
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