Effects of p-chloromercuribenzene sulfonate on water transport across the marsupial erythrocyte membrane
G. Benga,1 B.E. Chapman,2 H.V. Matei,1 C. Gallagher,2,3 D. Blyde,4 P.W. Kuchel2
1 Department of Cell and Molecular Biology, ‘‘Iuliu Hatieganu’’ University of Medicine Cluj-Napoca, 3400 Cluj-Napoca, Romania
2 Department of Biochemistry, University of Sydney
3 Taronga Zoo, Sydney, Australia
4 Western Plains Zoo, Dubbo, NSW, Australia
The eﬀects of exposure of red blood cells (RBC) of three species of marsupial to a mercury-containing sulfhydryl-modifying reagent, p-chloromercuribenzene sulfonate (PCMBS), on the water diﬀusional permeability (Pd) of their membranes were monitored by using an Mn2+-doping 1H nuclear magnetic resonance (NMR) technique at 400 MHz. For koala (Phascolarctos cinereus), RBC the maximal inhibition was reached at 37 C in 60 min with 1 mmol.l–1 PCMBS or in 15–30 min with 2 mmol. l–1 PCMBS. In contrast, in the case of red kangaroo (Macropus rufus) or swamp wallaby (Wallabia bicolor) RBC, maximal inhibition required an incubation of 90 min at 37 C with 2 mmol.l–1 PCMBS. For the RBC of all three species the value of maximal inhibition was very high, being 50–70% when measured at 25 C, 60–80% at 30 C and 60–70% at 37 C. The lowest values of Pd appeared to be around 2·10–3–3·10–3 cm.s–1 in the temperature range of 25–37 C. The mean value of the activation energy of water diﬀusion (Ea,d) was 20–25 kJ.mol–1 for control and 40 kJ.mol–1 for PCMBS-inhibited RBCs. These results show that marsupial RBC have a basal permeability to water similar to that previously reported for human RBC, but a higher value of the PCMBS-inhibitable water permeability. This indicates that the higher water permeability of marsupial RBC compared with human RBC is associated with a higher fraction of protein-mediated water permeability.