Maturation of membrane function: The permeability of the rat erythroblastic leukemic cell to water and to non-electrolytes

Abstract

The erythroblastic leukemia produced in Long‐Evans rats by the administration of 7, 8, 12 trimethylbenz (a) anthracene has been used as a model of the most immature form of the erythrocyte series. In conjunction with studies of the maturation of several other membrane functions, the permeability of this cell to water and to certain definitive non‐electrolytes was measured with osmotic methods. The hydraulic conductivity, L_p was 6.2 micro (minute)⁻¹, (atm)⁻¹ at 25°C, quite high and characteristic of mature erythrocytes, but different from values of 0.65 for immature myeloid cells. The effect of temperature provided an energy of activation of 4.4 kCal/mole, also typical of mature mammalian erythrocytes but again different from 13 to 18 kCal/mole for immature myeloid cells. Urea was compared to thiourea. The permeability coefficient for urea was 76.7 micra (minute)⁻¹ ± 13.8 (S. E.); the value for thiourea was 1.55 micra (minute)⁻¹ ± 0.18 (S. E.). Phloretin at 0.25 mM inhibited urea permeability by 90% with 50% inhibition occurring at 0.05 mM. Inhibition was reversible. Permeability to the glycols was also compatible with mature erythrocytes. We infer from these findings that the structure which underlies these basic, passive membrane functions is laid down early and persists after loss of nucleus and subsequent maturation.