Comparative studies of water permeability of red blood cells from humans and over 30 animal species: an overview of 20 years of collaboration with Philip Kuchel

NMR measurements of the diffusional permeability of the human adult red blood cell (RBC) membrane to water (P (d)) and of the activation energy (E (a,d)) of the process furnished values of P (d) similar to 4 x 10(-3) cm/s at 25 A degrees C and similar to 6.1 x 10(-3) cm/s at 37 A degrees C, and E (a,d) similar to 26 kJ/mol. Comparative NMR measurements for other species showed: (1) monotremes (echidna and platypus), chicken, little penguin, and saltwater crocodile have the lowest P (d) values; (2) sheep, cow, and elephant have P (d) values lower than human P (d) values; (3) cat, horse, alpaca, and camel have P (d) values close to those of humans; (4) guinea pig, dog, dingo, agile wallaby, red-necked wallaby, Eastern grey kangaroo, and red kangaroo have P (d) values higher than those of humans; (5) mouse, rat, rabbit, and small and medium size marsupials have the highest values of P (d) (> 8.0 x 10(-3) cm/s at 25 A degrees C and > 10.0 x 10(-3) cm/s at 37 A degrees C). There are peculiarities of E (a,d) values for the RBCs from different species. The maximum inhibition of diffusional permeability of RBCs induced by incubation with p-chloromercuribenzene sulfonate varied between 0 % (for the chicken and little penguin) to similar to 50 % (for human, mouse, cat, sheep, horse, camel, and Indian elephant), and similar to 60-75 % (for rat, guinea pig, rabbit, dog, alpaca, and all marsupials). These results indicate that no water channel proteins (WCPs) or aquaporins are present in the membrane of RBCs from monotremes (echidna, platypus), chicken, little penguin and saltwater crocodile whereas WCPs from the membranes of RBCs from marsupials have peculiarities.