THE ENTRANCE OF WATER INTO BEEF AND DOG RED CELLS

Abstract

The rate constants for diffusion of THO [radioactive water] across the red cell membrane of beef and dog, and the rate of entrance of water into the erythrocytes of these species under an osmotic pressure gradient have been measured. For water entrance into the erythrocyte by diffusion the rate constants are 0.10 [plus or minus] 0.02 msec. -1 (beef) and 0.14 [plus or minus] 0.03 msec.-1 (dog); the permeability coefficients for water entrance under a pressure gradient of 1 osmol./cm.3 are 0.28 cm.4 /osm., sec. (beef) and 0.72 cm.4/osm.,sec (dog). These values permit the calculation of an equivalent pore radius for the erythrocyte membrane of 4.1 A for beef and 7.4 A for dog. In the beef red cell the change in THO diffusion due to osmotically produced cell volume shifts has been studied. The resistance to THO diffusion increases as the cell volume increases. At the maximum volume, (1.06 times normal), THO diffusion is decreased to 0.84 times the normal rate. This change in diffusion is attributed to swelling of the cellular membrane.