title: Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVIII platypus (Ornithorhynchus anatinus) and saltwater crocodile (Crocodylus porosus).
abstract: As part of a programme of comparative measurements of Pd (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 approximately 6.3 microm. Pd was measured by using an Mn2+-doping 1H NMR (nuclear magnetic resonance) technique. The Pd (cm/s) values were relatively low: approximately 2.1 x 10(-3) at 25 degrees C, 2.5 x 10(-3) at 30 degrees C, 3.4 x 10(-3) at 37 degrees C and 4.5 at 42 degrees C for the platypus RBCs and approximately 2.8 x 10(-3) at 25 degrees C, 3.2 x 10(-3) at 30 degrees C, 4.5 x 10(-3) at 37 degrees C and 5.7 x 10(-3) at 42 degrees C for the crocodile RBCs. In parallel with the low water permeability, the Ea,d (activation energy of water diffusion) was relatively high, approximately 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.
authors.affiliation: First Laboratory of Genetic Explorations, Cluj County Emergency Hospital and Gheorghe Benga Foundation, Cluj Napoca, Romania. gbenga@gmail.com
authors.forename: Gheorghe
authors.initials: G
authors.lastname: Benga
authors.forename: Bogdan E
authors.initials: BE
authors.lastname: Chapman
authors.forename: Guy C
authors.initials: GC
authors.lastname: Cox
authors.forename: Philip W
authors.initials: PW
authors.lastname: Kuchel
mesh_terms: D000489:Alligators and Crocodiles / Q000097:blood*; D000818:Animals; D002463:Cell Membrane Permeability / Q000502:physiology*; D004058:Diffusion; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010987:Platypus / Q000097:blood*; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water