Comparative MMR studies of diffusional water permeability of red blood cells from different species. X. Camel (Camelus dromedarius) and alpaca (Lama pacos)

The diffusional water permeability (Pd) Of camel and alpaca red blood cells (RBCs) was measured by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulp honate (PCMBS). The values of Pd were, in the case of alpaca RBC approximat e to 4.6 x 10(-3) cm/s at 25 degrees C, 5.4 x 10(-3) cm/s at 30 degrees C, 6.6 x 10(-3) cm/s at 37 degrees C and 7.7 x 10(-3) cm/s at 42 degrees C. In case of camel RBC the values of Pd where approximate to 4.2 x 10(-3) cm/s at 25 degrees C, 5.3 x 10(-3) cm/s at 30 degrees C, 7.4 x 10(-3) cm/s at 37 degrees C and 9.0 x 10(-3) cm/s at 42 degrees C. Systematic studies on the effects of PCMBS on water diffusion in camel RBC indicated that the maxima l inhibition was reached in 45 min with 1-2 mm PCMBS. The values of maximal inhibition were around 47% at 25 degrees C and 68% at 30 degrees C for alp aca RBC and around 62% at 25 degrees C and 56% at 37 degrees C for camel RB C. The basal permeability to water of alpaca RBC was estimated at around 2. 6 x 10(-3) cm/s at 25 degrees C, 1.7 x 10(-3) cm/s at 30 degrees C and of c amel RBC as 1.8 x 10(-3) cm/s at 25 degrees C and 3.0 x 10(-3) cm/s at 37 d egrees C. The values of the activation energy of water diffusion (E-a,E-d) were around 23 kJ/mol for camel and 34 kT/mol for alpaca RBC. This suggests that in addition to the number of transport channels other features of the pathways might be important for defining the temperature dependence of the water permeability.