Stanisław Przestalski

Modifications of erythrocyte membrane hydration induced by organic tin compounds

A study on the effects of selected organic chlorides of tin on the extent of hydration of the lipid bilayer of erythrocyte ghosts from pig blood is presented. The following compounds were used, dibutyltin dichloride (DBT), tributyltin chloride (TBT), diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT). The degree of membrane hydration was measured by the ATR FTIR technique, which makes it possible to estimate the level of carbonyl and phosphate group hydration in lipids of membranes. Other measurements were made with a fluorescence technique involving a laurdan probe. Tin organic compounds caused dehydration of the lipid bilayer of ghosts in the region of the carbonyl groups. DBT and TBT produced weak dehydration in the region of the phosphate group, whereas DPhT and TPhT increased hydration. The results allow one to determine the location of organotin compounds within a membrane, and show that TBT penetrates the membrane the deepest and DBT the shallowest. Phenyl tin compounds penetrate membranes to an intermediate depth. The results obtained indicate that the destructive properties of the organometallic compounds depend mostly on their effect on hydration of the membrane.

Role of Hydrophobic and Hydrophilic Interactions of Organotin and Organolead Compounds with Model Lipid Membranes

Abstract The present study was conducted to clarify the mechanism of toxicity of organic compounds using lipid model membranes (liposomes and planar lipid membranes). The compounds studied were trialkyltin and trialkyllead chlorides, dialkyltin dichlorides and some inorganic forms of those metals. Two different (anionic and cationic) detergents were also used in the experiments to change the surface properties of liposomes. As a measure of interaction between the compounds studied and model membranes were the release of liposome bound praseodymium and the change in stability of planar membranes under the influence of those compounds. On the basis of the results obtained it was postulated that the mechanism of interaction between tin-and leadorganics and model lipid membranes is a combination of different factors featuring interacting sides. The most important properties determining the behaviour of organic compounds in the interaction were lipophilicity and polarity of different parts of the organics and the steric arrangement they can take in the medium. On the other hand, the surface potential of the lipid bilayer and the environment of the lipid molecules, that play a significant role in the availability of the lipid bilayer to the organics, were important factors in the interaction.

Adsorption of Phenyltin Compounds onto Phosphatidylcholine/Cholesterol Bilayers

Phenyltin compounds are known to be biologically active and, whan widely spread, are potentially hazardous. As their chemical structure suggests, they interact with the lipid fraction of the cell membrane. Their effect on the model phosphatidylcholine/cholesterol bilayer has been studied using fluorescence and 1H NMR techniques. The change in the fluorescein-PE fluorescence intensity indicates the amount of charge added by phenyltin compounds to the membrane surface. Although the presence of cholesterol alone does not alter membrane interface properties measured with fluorescein-PE, 1H NMR measurements show that lipid mobility is altered throughout the hydrophobic core of the membrane. Cholesterol in the phosphatidylcholine bilayer does not alter tetraphenyltin interaction with the membrane, though the effect of diphenyltin dichloride, penetrating deeply into the hydrophobic core of the membrane, is reduced when the amount of cholesterol in the membrane is increased, suggesting decreased compound adsorption. Triphenyltin chloride has a qualitatively different effect on the lipid bilayer, when observed using this fluorescence technique. The adsorption of triphenyltin onto the phosphatidylcholine/cholesterol membrane induces a lateral phase separation of membrane components. Since triphenyltin chloride is known to be adsorbed onto the interface of the lipid bilayer, this separation mechanism must originate in this region and does not seem to be electrostatic in origin. 1H NMR measurements have confirmed the observation that these two active phenyltin compounds interact with the phosphatidylcholine/cholesterol membrane differently, disrupting different regions of the bilayer to a different degree. Copyright

Stability of Model Membranes in the Presence of Organotin Compounds

The influence of tri- and di-alkyltins (TATs and DATs) as well as di- and triphenyltin compounds (DPhTs and TPhTs) on haemolysis of red blood cells (RBCs) and stability of planar lipid membranes (PLMs) has been studied. The results obtained show that the efficiency of TATs (trimethyl-, triethyl-, tri-n-propyl- and tributyl-tin chlorides) in destroying PLMs did not differ greatly when the compounds were studied in solutions of physiological pH (phosphate buffer, pH 7.4). A decrease in pH to 5.0 caused small changes in the efficiency of the three largest TAT molecules and a significant decrease in the efficiency of trimethyltin chloride. Both haemolytic and PLM experiments showed that the most active TAT was tri-n-propyltin chloride. The destructive action of DAT (dimethyl- and dibutyltin) and DPhT dichlorides was somewhat more differentiated. Dimethyltin dichloride (DMT) interaction with model membranes was a little weaker than that of DPhT and dibutyltin dichlorides and all these compounds influenced the model membranes to a lesser extent than TATs or TPhT. To bring about comparable haemolysis effects the dichlorides had to be used at much greater concentrations than the chlorides. The haemolytic properties of the dichlorides, especially of that of DMT, significantly increased in solution at pH 5.0. TPhT chloride interacted with model membranes similarly to TAT chlorides. Also, no great difference in efficiency of this compound was found for the two buffer solutions used. Copyright

Protective Effect of Quaternary Piperidinium Salts on Lipid Oxidation in the Erythrocyte Membrane

Abstract A new series of amphiphilic compounds with incorporated antioxidant functional group has been investigated. Piperidinium bromides, differing in the alkyl chain length (8, 10, 12, 14 and 16 carbon atoms in the chain) were synthesised to protect biological and/or model membranes against peroxidation and following negative consequences. Their antioxidant activity was studied with erythrocytes subjected to UV radiation. The salts used inhibited lipid oxidation in the erythrocyte membrane. The degree of this inhibition depended on the alkyl chain length of the bromide used and increased with increasing alkyl chain length. A comparison of the results obtained for piperidinium bromides with those obtained for the widely used antioxidant 3,5-di-t-butyl-4-hydroxytoluene (BHT) revealed that only two shortest alkyl chain salts were less efficient than BHT in protecting erythrocyte membranes. A similar comparison with antioxidant efficiency of flavonoids extracted from Rosa rugosa showed that they protected the membranes studied more weakly than the least effective eight-carbon alkyl chain piperidinium bromide. The three compounds of longest alkyl chains were the most active antioxidants. Their activities did not differ significantly.

A Synergistic Effect of Select Organotin Compounds and Ionic Surfactants on Liposome Membranes

Organometallic compounds and surfactants constitute a potential threat to the environment. For that reason we have embarked on a study of their joint action on membranes. Model lecithin liposome membranes were modified with the cationic surfactant trimethyldodecylammonium bromide or the anionic surfactant sodium dodecylsulfonate, and the effect of tripropyltin chloride on the process of calcium (Ca 2+ ) and praseodymium (Pr 3+ ) desorption from the liposome membrane was studied. Kinetic constants for the process of Ca 2+ ion desorption from lecithin liposome membranes were determined using the radiotracer method. The percentage of Pr 3+ ion desorption from liposome membranes was measured by the 1 H NMR method. Trimethyltin, triethyltin and tripropyltin alone caused increased Ca 2+ and Pr 3+ desorption from liposome membranes with increasing concentration of the compounds and alkyl chain length. For both the processes studied, a cationic surfactant brought about a lower effectiveness of tripropyltin and an anionic surfactant resulted in a higher effectiveness. The effect observed can be explained by changes in the surface charge of the membrane, induced by the surfactant modifiers and by the concomitant change in the partition coefficient of the organotin. The results obtained indicate a protective or harmful joint action of the surfactants used with tripropyltin on membranes.

Protection of erythrocytes against organometals-induced hemolysis.

The hemolytic toxicity of tributyllead (TBL) and triphenyllead (TPhL) chlorides and its prevention by dithiotreitol (DTT), diethylenetriaminepentamethylenephosphonic acid pentasodium (PMP) and sodium disulfide (Na2S) was studied. It was found that both TBL and TPhL efficiently hemolyzed pig erythrocytes when used in micromolar concentrations; tributyllead chloride being about twice more efficient than triphenyllead chloride. The hemolytic efficiency of these compounds was blocked by PMP, DTT and Na2S in a concentration-dependent manner. However, significant differences in antihemolytic efficiency of these compounds were found. Namely, DTT and Na2S were very efficiently protecting erythrocytes against the action of organoleads, while the PMP protection was weak. Also, differences between DTT and Na2S protective eficiency were found. They more efficiently prevented erythrocyte hemolysis by TPhL than by TBL. Moreover, erythrocytes were better protected against the action of TBL by Na2S than by DTT. Such differentiation may be connected with possible differences in localization of the organolead compounds and protective agents in the erythrocyte membrane. To check these possibilities a series of experiments was performed using the fluorescence technique and various fluorimetric probes. These measurements enabled to determine fluidity changes induced in erythrocyte membranes by the organoleads and the protective compounds and to formulate some remarks concerning the differences in the mechanism of interaction of the organoleads with these membranes.

Toxicity and model membrane modifying properties of organolead compounds

Department of Botany and Plant Physiology, Agricultural University, Cybulskiego 32, 50–205 Wroclaw,PolandThe influence of trialkylleads on haemolysis ofred blood cells (RBCs), growth of Spirodelaoligorrhiza and stability of planar lipid mem-branes (PLMs) at different pH of solution hasbeen studied. The results obtained show that theefficiency of trialkylleads (methyl-, ethyl-, pro-pyl- and butyl-lead chlorides) in modifying thephysiological and mechanical properties of theobjects studied depended both on pH of solutionand hydrophobicity of the compounds. Namely,it was found that this efficiency increased withpH of solution. The most significant increase wasobserved in PLM experiments. Also, the hydro-phobicity of trialkylleads influenced the proper-ties mentioned. The more hydrophobic a com-pound the greater was its haemolytic toxicity.The same applies to the physiological toxicityof the compounds, whose measure was 50%inhibition of plant growth. Generally, thesequence of modifying possibilities of the com-pounds studied at any pH of the solution was thefollowing:tributyllead >tripropyllead >triethyllead >trimethylleadA possible mechanism of the interaction oforganolead species with model and biologicalmembranes is discussed. Copyright # 2001John Wiley & Sons, Ltd.Keywords: triorganolead chlorides; erythrocytehaemolysis; physiological toxicity; planar lipidmembranes destabilization; interaction mechan-ism.

Direct or indirect influence of triphenyl‐lead on activity of Na+/K+‐ATPase

We have studied the effect of triphenyl-lead chloride on the lipid phase of erythrocyte membranes, on lipid monomolecular layers and Na + /K + -ATPase of the microsomal fraction of rat brain. It was found that the haemolytic effect induced by this compound occurs when its concentration exceeds 30 μM. The minimal lead concentration inducing measurable effects in monomolecular lecithin layers is about 1 μM. Inhibition of Na + /K + -ATPase activity begins at a concentration exceeding 0.5 μM. Maximum inhibition is observed at around 40 μM-a concentration at which haemolysis also occurs. It can thus be thought that at very low lead concentrations the main (or exclusive) role in modifying membrane function is played by direct interaction between lead and the sulphydryl groups of ATPase, whereas at higher concentrations two effects seem to overlap: direct interaction between lead and enzymic proteins via their sulphydryl groups and as indirect influence on the proteins via changes in the organization of the lipid phase of the membrane.

Different Effects of Di- and Triphenyltin Compounds on Lipid Bilayer Dithionite Permeabilization

Abstract Phenyltins are chemicals widely used in industry, hence their occurrence in the human environment is frequent and widespread. Such compounds include hydrophobic phenyl rings bonded to positively charged tin. This molecular structure makes them capable of adsorbing onto and penetrating through biological membranes, hence they are potentially hazardous. Two such compounds, diphenyltin and triphenyltin, show different steric constraints when interacting with the lipid bilayer. It has been demonstrated that these compounds are positioned at different locations within model lipid bilayers, causing dissimilarity in their ability to affect membrane properties. In this paper we present a study regarding the ability of these two phenyltins to facilitate the transport of S2O4-2 ions across the lipid bilayer, evaluated by a fluorescence quenching assay. In concentration range of up-to 60 μm those compounds do not affect lipid bilayer topology, when evaluated by vesicle size distribution. Both phenyltins facilitate the transfer of S2O4-2 across the model lipid bilayer, but the dependence of dithionite transport on phenyltin concentration is different for both. In principle, above 20 μm triphenyltin is more efficient in transfering ions across the lipid bilayer than diphenyltin.