The present work was done to determine the effect of temperature of the half-saturation constant (ø) and the maximum transport rate (K) of the facilitated diffusion of glycerol across the erythrocyte membrane of Peromyscus californicus.

Early qualitative erythrocyte permeability studies (Gryns, 1896; Hedin, 1897) revealed the wide range of non-electrolyte permeability rates across a cell membrane composed of lipid molecules. Theoretically, water-soluble non-electrolytes such as glycerol, ethylene glycol and erythritol would penetrate less rapidly than lipid-soluble non-electrolytes. It was thought that the rate of penetration of water-soluble non-electrolytes was inversely proportional to their molecular size and the penetration of lipid-soluble non-electrolytes was directly proportional to their lipid-solubility.

The present kinetic study of the permeability of rabbit erythrocytes has established that carrier systems are involved in the penetration of certain non-electrolytes. Saturation, competitive inhibition, and butanol inhibition kinetics were used to demonstrate the presence of carrier systems and the values of half-saturation constants (ø) were determined for the following water soluble non-electrolytes: glycerol, ethylene glycol, urea, and thiourea. These non-electrolytes are commonly used in permeability studies because they are relatively non-toxic and their small sizes allow penetration of the erythrocyte membrane within a reasonable length of time.