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Cell Biology International (2010) 34, 703–708 (Printed in Great Britain)

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Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVIII platypus (Ornithorhynchus anatinus) and saltwater crocodile (Crocodylus porosus)

Gheorghe Benga*¹, Bogdan E Chapman†, Guy C Cox‡ and Philip W Kuchel†

*First Laboratory of Genetic Explorations, Cluj County Emergency Hospital and Gheorghe Benga Foundation, ClujNapoca, Romania, †School of Biomolecular Sciences, University of Sydney, Sydney NSW, Australia, and ‡The Australian Key Center for Microscopy and Microanalysis, University of Sydney, Sydney NSW, Australia

As part of a programme of comparative measurements of P_d (diffusional water permeability) the RBCs (red blood cells) from an aquatic monotreme, platypus (Ornithorhynchus anatinus), and an aquatic reptile, saltwater crocodile (Crocodylus porosus) were studied. The mean diameter of platypus RBCs was estimated by light microscopy and found to be ∼6.3 μm. P_d was measured by using an Mn²⁺-doping 1H NMR (nuclear magnetic resonance) technique. The P_d (cm/s) values were relatively low: ∼2.1×10⁻³ at 25°C, 2.5×10⁻³ at 30°C, 3.4×10⁻³ at 37°C and 4.5 at 42°C for the platypus RBCs and ∼2.8×10⁻³ at 25°C, 3.2×10⁻³ at 30°C, 4.5×10⁻³ at 37°C and 5.7×10⁻³ at 42°C for the crocodile RBCs. In parallel with the low water permeability, the E_a,d (activation energy of water diffusion) was relatively high, ∼35 kJ/mol. These results suggest that “conventional” WCPs (water channel proteins), or AQPs (aquaporins), are probably absent from the plasma membranes of RBCs from both the platypus and the saltwater crocodile.

Key words: aquaporin, crocodile, diffusional water permeability, NMR, platypus, red blood cell

Abbreviations: A, surface area of the cell, AQP, aquaporin, E_a,d, activation energy of water diffusion, NMR, nuclear magnetic resonance, P_d, diffusional water permeability, RBCs, red blood cells, T_e, water diffusion exchange time, V, cell-water volume, WCP, water channel protein

¹To whom correspondence should be addressed (email gbenga@gmail.com).

Received 16 November 2009/22 February 2010; accepted 26 February 2010

Published as Cell Biology International Immediate Publication 26 February 2010, doi:10.1042/CBI20090430

© The Author(s) Journal compilation © 2010 Portland Press Limited