Red Cell Membrane Permeability Research Articles

The super sickling haemoglobin HbS‐Oman: a study of red cell sickling, K+ permeability and associations with disease severity in patients heterozygous for HbA and HbS‐Oman (HbA/S‐Oman genotype)

Studying different sickle cell genotypes may throw light on the pathogenesis of sickle cell disease (SCD). Here, the clinical profile, red cell sickling and K+ permeability in 29 SCD patients (15 patients with severe disease and 14 with a milder form) of HbA/S-Oman genotype were analysed. The super sickling nature of this Hb variant was confirmed. The red cell membrane permeability to K+ was markedly abnormal with elevated activities of Psickle , Gardos channel and KCl cotransporter (KCC). Results were consistent with Ca2+ entry and Mg2+ loss via Psickle stimulating Gardos channel and KCC activities. The abnormal red cell behaviour was similar to that in the commonest genotype of SCD, HbSS, in which the level of mutated Hb is considerably higher. Although activities of all three K+ transporters also correlated with the level of HbS-Oman, there was no association between transport phenotype and disease severity. The super sickling behaviour of HbS-Oman may obviate the need for solute loss and red cell dehydration to encourage Hb polymerisation, required in other SCD genotypes. Disease severity was reduced by concurrent α thalassaemia, as observed in other SCD genotypes, and represents an obvious genetic marker for prognostic tests of severity in young SCD patients of the HbA/S-Oman genotype.

P15: Nitric oxide scavenging by red blood cell microparticles

Cell derived Microparticles (MPs) are small phospholipid vesicles released from a variety of cells, such as platelets, red blood cells (RBCs) and white blood cells, or endothelial cells. Accumulating evidence shows that MPs are involved in many biological diseases. The clinical significance of MPs has been studied for years. Our studies focus on red blood cell MPs that are released during blood storage and post-transfusion. We have reviously shown that these MPs scavenge NO almost as fast as cell free hemoglobin, about 1000 times faster than red cell encapsulated hemoglobin. Reduced NO scavenging by cell-free hemoglobin compared to red cells is due limitations of external diffusion of NO to the red cell (including that through a cell-free zone that forms in the blood vessel pushing the red cells away from the endothelium where NO is made) and by finite red cell membrane permeability of NO. We have now explored the relative role of cell-free hemoglobin and hemoglobin encapsulated in microparticles formed during blood storage in scavenging NO. We have measured the NO consuming ability of free HbA and MPs in plasma of different age stored blood using a chemiluminescence-based assay. Our results show that both hemoglobin concentrations of free HbA and MPs increase along with blood aging. The proportion of hemoglobin concentration in MPs increases compared to cell-free hemoglobin as the blood ages. To explore the extent of NO scavenging by MP-encapsulated hemoglobin (MP-HbA) during blood transfusion, we have also modeled Nitric Oxide (NO) uptake by RBCs and MPs within a blood vessel using computer simulations. We found that membrane permeability appears to influence the rate of NO uptake by RBCs and MPs. In addition, the appearance of MPs in RBC cell free zone may significantly reduce NO bioavailability. To determine whether MPs do enter the cell-free zone, we have studied the effect of MPs on NO-mediated vasodilation with and without intravascular flow by using isolated micro vessels in a myograph apparatus. The data show that, similar to the case of cell-free hemoglobin and dissimilar to the case of red blood cells, flow does not substantially influence vessel tone when MP-HbA is present. Thus, MP-HbA probably does enter the cell-free zone. These data suggest that as little as 5 μ M MP-HbA can reduce NO bioavailability upon transfusion of old blood, an amount that would be present after transfusion of just 1–2 U. [Supported by HL098032]. Disclosure Nothing to disclose.

CHARACTERISTIC OF RESISTANCE OF ERYTHROCYTES IN CARDIOSURGICAL PATIENTS WITH VARIOUS DEGREE OF MANIFESTATION OF POSTPERFUSION HEMOLYSIS

The resistance of red cells to the mechanic, osmotic, and acid factors, as well as the permeability of red-cell membrane to low-molecular hydrophilic substances in patients with ischemic heart disease (IHD) with moderate (24 patients) and pronounced (13 patients) hemolysis after surgery under conditions of cardia bypass has been studied. It is found that the development of pronounced hemolysis (in contrast to the moderate one) is associated with the high permeability of the red-cell membrane before surgery at the reduced acid and mechanic resistance of cells, which decreases after surgery and combines with normalization of acid resistance of red cells with the red-cell membrane permeability kept at the initially high level. The osmotic resistance of red cells in IHD patients is increased regardless of the level of hemolysis and the stage of the study, and its minimal level is observed only in patients with moderate hemolysis before surgery.

A novel erythroid anion exchange variant (Gly796Arg) of hereditary stomatocytosis associated with dyserythropoiesis

Stomatocytoses are a group of inherited autosomal dominant hemolytic anemias and include overhydrated hereditary stomatocytosis, dehydrated hereditary stomatocytosis, hereditary cryohydrocytosis and familial pseudohyperkalemia. We report a novel variant of hereditary stomatocytosis due to a de novo band 3 mutation (p. G796R-band3 CEINGE) associated with a dyserythropoietic phenotype. Band 3 genomic analysis, measurement at of hematologic parameters and red cell indices and morphological analysis of bone marrow were carried out. We then evaluated the red cell membrane permeability and ion transport systems by functional studies of the patient's erythrocytes and Xenopus oocytes transfected with mutated band 3. We analyzed the red cell membrane tyrosine phosphorylation profile and the membrane association of the tyrosine kinases Syk and Lyn from the Src-family-kinase group, since the activity of the membrane cation transport pathways is related to cyclic phosphorylation-dephosphorylation events. The patient showed mild hemolytic anemia with circulating stomatocytes together with signs of dyserythropoiesis. Her red cells displayed increased Na(+) content with decreased K(+)content and abnormal membrane cation transport activities. Functional characterization of band 3 CEINGE in Xenopus oocytes showed that the mutated band 3 is converted from being an anion exchanger (Cl(-), HCO(3)(-)) to being a cation pathway for Na(+) and K(+). Increased tyrosine phosphorylation of some red cell membrane proteins was observed in diseased erythrocytes. Syk and Lyn membrane association was increased in the patient's red cells compared to in normal controls, indicating perturbation of phospho-signaling pathways involved in cell volume regulation events. Band 3 CEINGE alters function from that of anion exchange to cation transport, affects the membrane tyrosine phosphorylation profile, in particular of band 3 and stomatin, and its presence during red cell development likely contributes to dyserythropiesis.

Chocolate Intake Associated with Failed Labeling of 99mTc Red Blood Cells

Red blood cells (RBC) labeled in vivo with (99m)Tc-pertechnetate are used worldwide in nuclear medicine departments. Here, we present a case of (99m)Tc-RBC labeling failure associated with chocolate intake in a 25-y-old woman, resulting in uninterpretable images. Because of this clinical observation, we performed in vitro RBC labeling on blood samples from volunteers after they consumed chocolate. Chocolate intake inhibited the labeling rate, compared with the control condition, and significantly increased the (99m)Tc free fraction (34.1% +/- 11.3% vs. 14.0% +/- 1.2%). We cannot explain how this interaction could occur, but cacao components are known to modulate red cell and plasma oxidoreductive status and to modify red cell membrane permeability and plasticity. Therefore, for patients who can be considered likely to consume chocolate, such as young patients, we recommend that they limit their consumption of chocolate for 12 h before RBC labeling.

Erythrocyte Glut1 Triggers Dehydroascorbic Acid Uptake in Mammals Unable to Synthesize Vitamin C

Of all cells, human erythrocytes express the highest level of the Glut1 glucose transporter. However, the regulation and function of Glut1 during erythropoiesis are not known. Here, we report that glucose transport actually decreases during human erythropoiesis despite a >3-log increase in Glut1 transcripts. In contrast, Glut1-mediated transport of L-dehydroascorbic acid (DHA), an oxidized form of ascorbic acid (AA), is dramatically enhanced. We identified stomatin, an integral erythrocyte membrane protein, as regulating the switch from glucose to DHA transport. Notably though, we found that erythrocyte Glut1 and associated DHA uptake are unique traits of humans and the few other mammals that have lost the ability to synthesize AA from glucose. Accordingly, we show that mice, a species capable of synthesizing AA, express Glut4 but not Glut1 in mature erythrocytes. Thus, erythrocyte-specific coexpression of Glut1 with stomatin constitutes a compensatory mechanism in mammals that are unable to synthesize vitamin C.

Induction of GLUT1 during Erythropoiesis Triggers a Switch from Glucose to DHA Uptake in Vitamin C-Defective Mammals.

Glucose provides a key supply of energy and carbon and its transport is achieved via multimembrane-spanning glucose transporters (GLUTs). The human erythrocyte is the cell type expressing the highest level of the GLUT1 glucose transporter, harboring greater than 200,000 molecules per cell. We now demonstrate that GLUT1 transcripts increase by 3-logs during erythropoiesis and high GLUT1 surface expression is observed following passage through the basophilic erythroblast stage. Paradoxically though, glucose transport significantly decreases. As GLUT1 also transports L-dehydroascorbic acid (DHA), the oxidized form of ascorbic acid (AA), transport of this molecule was assessed and indeed, it increases dramatically during erythropoiesis. The switch from glucose to DHA transport is coupled to the physical association of GLUT1 with stomatin, an integral erythrocyte membrane protein. We find that stomatin inversely regulates the relative transports of glucose and DHA by GLUT1. Moreover, in a patient with overhydrated hereditary stomatocytosis, a rare genetic disorder of red cell membrane permeability wherein stomatin is absent, glucose uptake is significantly higher but there is a concomitant 50% reduction in DHA transport. Intriguingly, erythrocyte-specific DHA transport is not conserved amongst all mammalian species; we did not detect GLUT1 on mature murine erythrocytes where DHA uptake is minimal. Notably though, humans differ from the vast majority of the greater than 5,000 mammalian species in that they are unable to synthesize ascorbic acid from glucose. This trait is shared only with other higher primates, guinea pigs and and fruit bats. We have determined that erythrocyte GLUT1 expression and associated DHA transport are specific features of these diverse ascorbic acid-deficient mammals. Within the primate order, defective ascorbic acid synthesis is due to an inactivation of the L-gulonolactone oxidase (GLO) enzyme at the Haplorrhini-Strespsirrhini split. In accord with the data presented above, we find that erythrocyte GLUT1 expression and associated DHA transport are characteristic of erythrocytes from primates within the Haplorrhini suborder but not Strepsirrhini lemurs. Thus, the erythrocyte-specific co-expression of GLUT1 and stomatin constitutes a compensatory mechanism in mammals that are unable to synthesize the essential ascorbic acid metabolite.

Red cell membrane CO 2 permeability in normal human blood and in blood deficient in various blood groups, and effect of DIDS

The red cell membrane has an exceptionally high permeability for CO 2, P CO2 ≈ 0.15 cm/s, which is two to three orders of magnitude greater than that of some epithelial membranes and similarly greater than the permeability of the red cell membrane for HCO 3 –. As shown previously, this high P CO2 can be drastically inhibited by 10 μM 4,4′-diisothiocyanato-2,2′-stilbenedisulfonate (DIDS), indicating that membrane proteins may be involved in this high gas permeability. Here, we have studied the possible contribution of several blood group proteins to CO 2 permeation across the red cell membrane by comparing P CO2 of red cells deficient in specific blood group proteins with that of normal red cells. While P CO2 of normal red cells is ~0.15 cm/s and that of Fy null and Jk null red cells is similar, P CO2's of Colton null (deficient in aquaporin-1) and Rh null cells (deficient in Rh/RhAG) are both reduced to about 0.07 cm/s, i.e. to about one half. In addition, the inhibitory effect of DIDS is about half as great in Rh null and in Colton null red cells as it is in normal red cells. We conclude that aquaporin-1 and Rh/RhAG proteins contribute substantially to the high permeability of the human red cell membrane for CO 2. Together these proteins are responsible for 50% or more of the CO 2 permeability of red cell membranes. The CO 2 pathways of both proteins can be partly inhibited by DIDS, which is why this compound very effectively reduces membrane CO 2 permeability.

The hereditary stomatocytoses: genetic disorders of the red cell membrane permeability to monovalent cations

The hereditary stomatocytoses are mostly accounted for by genetic disorders of red cell membrane permeability to monovalent cations. These conditions, all very rare, are comprised of a hemolytic anemia, frequently macrocytosis, and the presence of abnormally shaped red blood cells. The key test for diagnosis is osmotic gradient ektacytometry, which measures the osmotic resistance and hydration of the red blood cell; the curve depicting the temperature dependence of the cation leak is also important. Syndromes include familial pseudohyperkalemia (FP), which is devoid of hematological features, dehydrated hereditary stomatocytosis (DHS), and overhydrated hereditary stomatocytosis (OHS). Some forms of DHS may be a pleiotropic, showing pseudohyperkalemia and/or perinatal edema. Perinatal edema, if not properly treated, may be lethal but may also resolve spontaneously prior to or shortly after birth and never reappear. Hereditary cryohydrocytosis, type 1 (CHC 1) is characterized by a dramatic resumption of the leak in vitro as the temperature approaches 0°C; cell hydration seems unaltered. In OHS, stomatin, a membrane protein, is sharply reduced; however, this is a secondary event and the primarily mutated protein remains unknown. Hereditary cryohydrocytosis, type 2 (CHC 2) presents similar to OHS, except that the leak dramatically increases close to 0°C. In addition, hematological manifestations are associated with neurological disorders. Of critical practical importance is that splenectomy in DHS or OHS causes thromboembolic events that may be fatal. The genes involved in hereditary stomatocytoses have yet to be identified. Apart from the 16q24-qter locus, related to subsets of DHS and FP, and a chromosome 2 locus assigned to a single case of FP, gene mapping has been difficult. The eventual discovery of individual genes will clarify complicated classification of the stomatocytoses, now based solely on phenotype.

Sickle red cell dehydration: mechanisms and interventions.

A critical link between the single molecular defect in sickle cell anemia and the extensive pathology of this disease is the reversible increase in red cell membrane permeability generated by hemoglobin S polymers in the deoxygenated state. This permeability, usually described as P (sickle), triggers a chain of events in which two constitutive transporters of the red cell membrane become activated-the recently cloned intermediate conductance, Ca 2+ -sensitive K channel, and the electroneutral K:Cl cotransporter-leading to sickle cell dehydration. This article reviews knowledge of the dehydration mechanism, stressing the marked heterogeneity of dehydration rates in sickle cell populations, and discusses recent contributions to understanding of the function and regulation of P (sickle), Ca 2+ -sensitive K channel, and K:Cl cotransporter, and of therapies targeted at these transporters.

Interaction of palytoxin with red cells: Structure-function studies

Palytoxin (PTX), a potent toxin isolated from the marine soft coral Palythoa tuberculosa increases the cationic permeability of red cell membranes and inhibits the (Na+ ,K+)-activated ATPase, effects that are completely reversed by ouabain. It has also been shown to compete with ouabain for a binding site and it has been suggested that it binds to the Na+,K+-pump molecule in cells. In a search for analogues of PTX that would bind covalently and could thus be used to identify and characterize the binding site, we have used compounds which differed from PTX at one end or at both ends simultaneously. In order to determine whether these derivatives could be used to replace palytoxin, we tested their potency to induce an increased cation flux, compete with ouabain for its binding site, and inhibit the isolated, purified (Na+,K+-ATPase). The results obtained indicate that departures from the PTX structure at one end or at both ends simultaneously substantially decrease the ability of the compounds to increase the cationic permeability of red blood cells and to inhibit the (Na+,K+-ATPase). These actions were found to be com- pletely reversed by ouabain, but the analogues are two to three orders of magnitude less potent that PTX in competing with ouabain for its binding site. These results suggest that both ends of the palytoxin molecule participate in the interactions of the toxin with its receptor and that modifications in these regions of the molecule produce significant alterations in its binding and subsequent action on red cell membranes.

Rheumatological complications of sickle cell disease

Haemoglobin consists of two beta chains, two alpha chains and four haem molecules. Normal human haemoglobin is designated haemoglobin (Hb) A. Genetic mutations of the gene encoding the beta chain may result in a single amino acid substitution, or amino acid deletion. More rarely, a point mutation in the globin chain termination codons results in elongated chains, or 'frame shift' mutations (from the loss of a single nucleotide base) alter all the subsequent genetic code triplets. The result of such mutations depends on the effect on the solubility, stability and 02 affinity of the haemoglobin complex. In sickle cell haemoglobin (Hb S) there is a point mutation of the gene encoding for the beta chain, resulting in the substitution of valine for glutamic acid at position 6. In the heterozygote (sickle cell trait) there is a mixture of Hb A and Hb S. In the homozygote (sickle cell anaemia) the majority of the haemoglobin is Hb S, with some fetal haemoglobin (Hb F). Hb S undergoes liquid crystal formation in hypoxic conditions, and the molecules aggregate in rod-like structures that then form into helices. The presence of other types of haemoglobin affects this process: for instance Hb F is excluded from the sickling process, and high Hb F concentration leads to less sickling. The crystallization of Hb S molecules causes red cell membrane damage and the red cells assume the characteristic sickle cell morphology. The process is reversible, but with increasing loss of red cell membrane and reduced red cell membrane permeability, the cell becomes irreversibly sickled; this leads to reduced red cell survival secondary to mechanical fragility and loss of membrane deformability (Mohandas et al, 1979). The sickled red cells aggregate in the microvasculature, resulting in increased blood viscosity, reduced blood flow, vascular stasis, and hence more hypoxia. More red cells sickle and the process accelerates leading, in some cases, to tissue infarction. Hb C has a lower solubility than Hb A, and in homozygous Hb C disease there is a tendency for the haemoglobin to crystallize. The resultant increase in red cell fragility and destruction in the microvasculature leads to a mild

Effect of Salicylate on Serum Protein Binding and Red Blood Cell Uptake of Acetazolamide In Vitro

The diffusion of acetazolamide from buffered saline and buffered albumin solutions into human erythrocytes has been characterized. A model was developed for describing the effects of both intra- and extracellular binding on the approach to distributional equilibrium. Unbound acetazolamide entered the cells via an apparent first-order process at a rate that was unaffected by salicylate at a therapeutic concentration of 200 μg/mL. Salicylate concentrations ranging from ~100 to 400 μg/mL were, however, extremely effective in displacing acetazolamide from its serum protein binding sites. Free fractions of acetazolamide in human serum were found to increase by an order of magnitude as salicylate concentrations approached 400 μg/mL, thereby greatly increasing the concentration of unbound drug available for passive diffusion into cells. The results indicate that while competitive binding effects, which may alter unbound drug concentration–time profiles and potentially impact on toxicity, do occur, alterations in red cell membrane permeability, which could adversely affect carbon dioxide transport, are not of significance.

Interspecies variability in propylene glycol dinitrate-induced methemoglobin formation

Interspecies variability of propylene glycol dinitrate (PGDN)-induced methemoglobin formation was studied in vitro employing erythrocytes from four separate species. The net rate of methemoglobin formation was significantly different among species with dog > guinea pig > rat ≥ human. This order of susceptibility was maintained in stroma-free hemolysates, indicating that interspecies variability was not a reflection of differences in red cell membrane permeability or intracellular transport of PGDN. The erythrocytic enzymes, catalase, superoxide dismutase, glutathione peroxidase, 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, methemoglobin reductase, and glutathione- S-transferase, were assayed by adaptation of existing methods to a centrifugal analyzer. The above enzymes were removed from hemoglobin derived from each species and the order of susceptibility to PGDN-induced methemoglobin formation remained essentially the same with dog > guinea pig > human = rat. However, the net rate of PGDN-mediated oxidation of hemoglobin to methemoglobin increased in purified hemoglobin preparations from each species. These results demonstrate that there is species variability in the net rate of PGDN-mediated methemoglobin formation. Total enzyme activity in erythrocytes may contribute to reduction in the net rate of methemoglobin formation. However, the primary determinant of the net rate of methemoglobin formation induced by PGDN appears to be the structure of each hemoglobin molecule.

Polyamines do not inhibit erythrocyte ATPase activities

To test whether physiologic elevation of red cell polyamine levels might explain Na pump inhibition in sickle cells or uremic red cells, we have studied the effect of putrescine, spermidine and spermine on red cell membrane ATPase and Na-K active transport. Measurement of the ouabain-sensitive influx of 86Rb into intact cells showed no effect of spermine. However, cells became depleted of ATP during incubation with spermine. By 48 h, the cells showed substantial potassium loss and moderate sodium gain. Because the low permeability of red cell membranes for polyamines might have obscured some direct effects on intracellular processes, we measured active transport of 22Na out of red cell ghosts that had been resealed in the presence of 5 mmol/1 spermine. In addition, we measured the Na-K, Mg, and Ca ATPase activities of broken membrane preparations in the presence of spermine, spermidine and putrescine. Polyamines had no direct effect on cation transport in red cells, although possible adverse effects on red cell metabolism could have a secondary effect on cation regulation.

Determination of human erythrocyte membrane hydraulic conductivity

A method of determining the osmotic water permeability of red cell membranes is described. This method is based on the rate of cell volume change induced by the perturbation of the osmotic environment of the cells and the paralleling change in light scattering by the cells. The method requires as little as 0.3 ml of blood and utilizes commercially available equipment. The value for the hydraulic conductivity of the human red cell membrane determined by this new technique is 1.56 ± 0.04 x 10 -11 cm 3/dyne sec, in good agreement with other techniques. These studies show that the hydraulic conductivity of the human erythrocyte membrane does not depend on the degree cell volume change when the cells are shrunk from their isotonic volume by 15, 20, or 25%. However, the Lp increases 50% when the cells are swollen 25%. The small amounts of blood required and the ready availability of the equipment necessary for the technique makes it now possible for many laboratories to make Lp determinations on normal or abnormal erythrocyte membrane as a means of more fully describing the permeability properties of the cell membrane.

Red cell permeability effect on the mean transit of an indicator transported through an organ by red cells and plasma.

When an indicator that permeates red blood cells with an equilibration time of the order of the mean transit time of the indicator through an organ is bolus injected solely into the plasma inflow to that organ, the mean transit time of the indicator is greater than it is when the indicator is injected preequilibrated between the plasma inflow and the red cell inflow. The mean transit time for equilibrated entry is in turn greater than that for indicator injected solely into the red cell inflow. A simplified method of calculation of this effect is given in the present paper; it requires only a model solution for the indicator steady state as distinguished from a more complicated time-dependent solution. The dependence of the effect on red cell membrane permeability allows this permeability to suitable indicators to be deduced. The method was applied to existing data on urea and thiourea passage through the dog kidney.

Red Cell Membrane Permeability Deduced from Bulk Diffusion Coefficients

The permeability coefficients of dog red cell membrane to tritiated water and to a series of[(14)C]amides have been deduced from bulk diffusion measurements through a "tissue" composed of packed red cells. Red cells were packed by centrifugation inside polyethylene tubing. The red cell column was pulsed at one end with radiolabeled solute and diffusion was allowed to proceed for several hours. The distribution of radioactivity along the red cell column was measured by sequential slicing and counting, and the diffusion coefficient was determined by a simple plotting technique, assuming a one-dimensional diffusional model. In order to derive the red cell membrane permeability coefficient from the bulk diffusion coefficient, the red cells were assumed to be packed in a regular manner approximating closely spaced parallelopipeds. The local steady-state diffusional flux was idealized as a one-dimensional intracellular pathway in parallel with a one-dimensional extracellular pathway with solute exchange occurring within the series pathway and between the pathways. The diffusion coefficients in the intracellular and extracellular pathways were estimated from bulk diffusion measurements through concentrated hemoglobin solutions and plasma, respectively; while the volume of the extracellular pathway was determined using radiolabeled sucrose. The membrane permeability coefficients were in satisfactory agreement with the data of Sha'afi, R. I., C. M. Gary-Bobo, and A. K. Solomon (1971. J. Gen. Physiol. 58:238) obtained by a rapid-reaction technique. The method is simple and particularly well suited for rapidly permeating solutes.

Probability Density Function of the Red Cell Membrane Permeability Coefficient

The distribution of a random variable is determined by the probability density functions (PDF) of all other random variables with which the variable in question is jointly distributed. If the PDF of the random variable of interest is normal, or skewed normal, then the distributions with which it is jointly distributed determine its mean and standard deviation. In the case described here (where hemolysis time of the red blood cell is a function of the permeability coefficient and geometric variables of the cell) the mean and standard deviation of the permeability coefficient and the known distributions of the geometric variables on which the hemolysis time depends determine a predicted distribution of hemolysis time. An observed distribution of the hemolysis time is obtained spectrophotometrically. By choosing the mean and standard deviation of the permeability coefficient so that the predicted PDF of the hemolysis time matches the observed PDF best by least-squares criterion, the complete distribution of the permeability coefficient is determined.

Patterns of nonelectrolyte permeability in human red blood cell membrane.

The permeability of human red cell membrane to 90 different molecules has been measured. These solutes cover a wide spectrum of nonelectrolytes with varying chemical structure, chain length, lipid solubility, chemical reactive group, ability to form hydrogen bonds, and other properties. In general, the present study suggests that the permeability of red cell membrane to a large solute is determined by lipid solubility, its molecular size, and its hydrogen-bonding ability. The permeability coefficient increases with increasing lipid solubility and decreasing ability to form hydrogen bonds, whereas it decreases with increasing molecular size. In the case of small solutes, the predominant diffusion factor is steric hindrance augmented by lipid solubility. It is also found that replacement of a hydroxyl group by a carbonyl group or an ether linkage tends to increase permeability. On the other hand, replacement of a hydroxyl group by an amide group tends to decrease the permeability coefficient.