Sodium permeability coefficient

Fig u re 3 (A) Effect of temperature on sodium permeability coefficient across excised human skin in passive ( ) and anodal iontophoresis (O) at 0.38 mA/cm. (B) Effect of temperature on cyclosporin A permeability coefficient across excised human skin in passive ( ) and anodal iontophoresis (O) at 0.38 mA/cm. (From Ref 62.)... 

Another relatively new lipophilicity scale proposed for use in ADME studies is based on MEKC [106]. A further variant is called BMC and uses mobile phases of Brij35 [polyoxyethylene(23)lauryl ether] [129]. Similarly, the retention factors of 16 P-blockers obtained with micellar chromatography with sodium dodecyl sulfate as micelle-forming agent correlates well with permeability coefficients in Caco-2 monolayers and apparent permeability coefficients in rat intestinal segments [130]. 

We can now consider some typical nutrient solutes like amino acids and phosphate. Such molecules are ionized, which means that they would not readily cross the permeability barrier of a lipid bilayer. Permeability coefficients of liposome membranes to phosphate and amino acids have been determined [46] and were found to be in the range of 10 11 -10 12 cm/s, similar to ionic solutes such as sodium and chloride ions. From these figures one can estimate that if a primitive microorganism depended on passive transport of phosphate across a lipid bilayer composed of a typical phospholipid, it would require several years to accumulate phosphate sufficient to double its DNA content or pass through one cell cycle. In contrast, a modern bacterial cell can reproduce in as short a time as 20 min. 

Fig. 19. Comparison of molecular weight-normalized values of the permeability coefficients of biological membranes with similar values determined for the polyelec-trolyte complex membrane of poly(sodium styrenesulfonate) (NaSS)-poly(4-vinylben-zyltrimethylammonmm chloride) (PVBMA)70 A Aminopyrine,...

Movement of penetrants across the mucous membranes is by diffusion. At steady state, the amount of a substance crossing the tissue per unit of time is constant and the permeability coefficients are not influenced by the concentration of the solutions or the direction of nonelectrolyte transfer. As in the epidermis of the skin, the pathways of permeation through the epithelial barriers are intercellular rather than intracellular. The permeability can be enhanced by the use surfactants such as sodium lauryl sulfate (a cationic surfactant). An unsaturated fatty acid, oleic acid, in a propylene glycol vehicle can act as a penetration enhancer for diffusion of propranolol through the porcine buccal mucosa in vitro. Delivery of biopharmaceuticals across mucosal surfaces may offer several advantages over injection techniqnes, which include the following ... 

We measured the permeability of rabbit sclera to a series of fluorescently labeled hydrophilic compounds with a wide range of molecular weights and radii. Sodium fluorescein, the smallest compound, had the highest permeability coefficient, whereas 150 kDa dextran, which had the largest molecular radius, had the lowest permeability coefficient. Our rabbit permeability data was quite similar to the reported permeability of human sclera. Bovine scleral permeability was less than that of the rabbit or human (Table 1). 

Permeability coefficients in this article are different from permeabihty coefficients in another related article (Hatanaka et al., 1990) because different hairless rat strains were used. The permeabihty coefficients for diclofenac sodium, dopamine hydrochloride, isoproterenol hydrochloride, indomethadn, and water were reported in the... 

Relative Selectivity of the Sodium Channel Ratios of Permeability Coefficient with Respect to Na of Ions Passing through the Early Na Channel of Axons... 

Sodium cocoyl isethionate (%) Porcine skin permeability coefficient (X 10 cm/h) Hummi skin TEWL (g/m h)... 

Example 3.4.5 Calculate the membrane mass-transfer coefficients and the permeability coefficients of two solutes, sodium sulfate and sucrose, through a microporous light denitrated cellulose membrane whose properties, along with those of the two solutes, are provided below (Lane and Higgle, 1959). The temperature is 20 °C, and dilute aqueous solutions are under consideration with essentially no convection through the membrane. For sodium sulfate M = 142 diffusion coefficient in water = 7.7 x 10 cm /s density />, = 2.698 g/cm. For sucrose Mj = 342 diffusion coefficient in water =... 

The permeability tests for alkali metal ions in the aqueous solution were also conducted. When an aqueous salt solution moves to cell 2 through the membrane from cell 1, the apparent diffusion coefficient of the salt D can be deduced from a relationship among the cell volumes Vj and V2, the solution concentration cx and c2, the thickness of membrane, and time t6 . In Table 12, permeabilities of potassium chloride and sodium chloride through the 67 membrane prepared by the casting polymerization technique from the monomer solution in THF or DMSO are compared with each other and with that the permeability through Visking dialyzer tubing. The... 

Using liposomes made from phospholipids as models of membrane barriers, Chakrabarti and Deamer [417] characterized the permeabilities of several amino acids and simple ions. Phosphate, sodium and potassium ions displayed effective permeabilities 0.1-1.0 x 10 12 cm/s. Hydrophilic amino acids permeated membranes with coefficients 5.1-5.7 x 10 12 cm/s. More lipophilic amino acids indicated values of 250 -10 x 10-12 cm/s. The investigators proposed that the extremely low permeability rates observed for the polar molecules must be controlled by bilayer fluctuations and transient defects, rather than normal partitioning behavior and Born energy barriers. More recently, similar magnitude values of permeabilities were measured for a series of enkephalin peptides [418]. 

Figure 5.5 Water permeability as a function of sodium chloride permeability for membranes made from cellulose acetate of various degrees of acetylation. The expected rejection coefficients for these membranes, calculated for dilute salt solutions using Equation (5.6),...

Furthermore, these characterizations will be completed in determining mass transfer parameters a and Ps, Cconv and Jdiff, respectively, the reflection coefficient and the solute permeability of the membranes, the part of solute mass transfer dedicated to convection and Jam the part of mass transfer dedicated to hydration-diffusion, for two synthetic chlorides and sulphates sodium salts solutions under different concentrations, 10-3 and 10-1 M. 

According to the Onsager s relations, three coefficients are to be determined. They are the passive permeability to sodium ZNa, the metabolic reaction coefficient if there is no sodium transport Zr, and the cross-coefficient between the chemical reaction and the sodium flow ZNar. The linear nonequilibrium thermodynamics formulation for the active transport of sodium and the associated oxygen consumption in frog skin and toad urinary bladders are studied experimentally. Sodium flow JNa is taken as positive in the direction from the outer to the inner surface of the tissue. The term JT is the rate of suprabasal oxygen consumption assumed to be independent of the oxygen consumption associated with the metabolic functions. 

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