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PubMed1986

Structural characterization of the ATP-hydrolyzing portion of the coated vesicle proton pump.

The ATP-hydrolyzing portion of the proton pump from clathrin-coated vesicles (isolated from calf brain) was solubilized with three nondenaturing detergents (cholate, octyl glucoside, and Triton X-100). The hydrodynamic properties of the solubilized (Mg2+)-ATPase were then determined by sedimentation analysis in H2O and D2O and gel filtration on Sepharose 4B. The coated vesicle (Mg2+)-ATPase migrated under all conditions as a single peak of activity. In cholate, the sedimentation coefficient (S20,w), Stokes radius (a), and partial specific volume (vc) were 8.25 (+/- 0.20) S, 68 (+/- 2) A, and 0.71 (+/- 0.03) cm3/g, respectively. In octyl glucoside and Triton X-100 these values were respectively 7.90 (+/- 0.20) and 7.45 (+/- 0.20) S, 68 (+/- 3) and 101 (+/- 5) A, and 0.74 (+/- 0.03) and 0.75 (+/- 0.03) cm3/g. Application of the Svedberg equation to these data gave a molecular weight for the protein-detergent complex of 217,000 +/- 21,000 (cholate), 234,000 +/- 26,000 (octyl glucoside), and 337,000 +/- 40,000 (Triton X-100). Assuming the protein binds one micelle of detergent, these values correspond to a protein molecular weight of 215,000 +/- 21,000 (cholate), 226,000 +/- 26,000 (octyl glucoside), and 247,000 +/- 40,000 (Triton X-100). The cholate-solubilized, gradient-purified (Mg2+)-ATPase, when combined with a 100,000 g pellet fraction, could be reconstituted by dialysis into phospholipid vesicles which displayed ATP-dependent proton uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1976

Characterization of the recombination reaction of rhodopsin.

The kinetics of recombination of 11-cis-retinal with bleached rod outer segments and sodium cholate solubilized rhodopsin have been investigated. At neutral pH, it was found that bleached rod outer segments in the presence of an excess of 11-cis-retinal follow pseudo-first-order kinetics. The results suggest the second-order formation of an intermediate addition compound followed by a first-order dehydration step to form a protonated aldimine linkage. In addition, at pH values above 7.5 or below 6.5 the kinetics of recombination are complex, indicating the formation of a molecular species inactive in recombination which is in equilibrium with the active form of opsin. Based upon the observed rate constants as a function of pH, a scheme is presented to describe the recombination reaction in bleached rod outer segments. The kinetics of recombination of sodium cholate solubilized opsin were also analyzed. In terms of formation of an intermediate addition compound and subsequent dehydration, the values for the individual rate constants for both bleached rod outer segments and cholate-solubilized opsin were found to compare very favorably. These results demonstrate that the sodium cholate (2 mg/ml) maintains opsin in a conformation very similar to that in the rod outer segment membrane and suggest that the cholate-opsin complex is an excellent model system for studies on opsin-membrane interactions.

Animals↗
PubMed2006

Solvent-induced amphiphilic molecular baskets: unimolecular reversed micelles with different size, shape, and flexibility.

Amphiphilic molecular baskets were obtained by attaching facially amphiphilic cholate groups to a covalent scaffold (calix[4]arene or 1,3,5-2,4,6-hexasubstituted benzene). In a solvent mixture consisting of mostly a nonpolar solvent (i.e., CCl4) and a polar solvent (i.e., DMSO), the hydrophilic faces of cholates turned inward to form a reversed-micelle-like conformer whose stability was strongly influenced by the number of the cholates and the topology of the scaffold. Preferential solvation of the hydrophilic faces of cholates within the molecule by the polar solvent was cooperative and gave the fundamental driving force to the conformational change. The reversed-micelle-like conformer was most stable in structures that allowed multiple cholates to form a microenvironment that could efficiently enrich the polar solvent molecules from the bulk solvent mixture.

Journal Article↗
PubMed1987

Solubilization of lipids from hamster bile-canalicular and contiguous membranes and from human erythrocyte membranes by conjugated bile salts.

We have demonstrated in vitro the efficacy of the taurine-conjugated dihydroxy bile salts deoxycholate and chenodeoxycholate in solubilizing both cholesterol and phospholipid from hamster liver bile-canalicular and contiguous membranes and from human erythrocyte membrane. On the other hand, the dihydroxy bile salt ursodeoxycholate and the trihydroxy bile salt cholate solubilize much less lipid. The lipid solubilization by the four bile salts correlated well with their hydrophobicity: glycochenodeoxycolate, which is more hydrophobic than the tauro derivative, also solubilized more lipid. All the dihydroxy bile salts have a threshold concentration above which lipid solubilization increases rapidly; this correlates approximately with the critical micellar concentration. The non-micelle-forming bile salt dehydrocholate solubilized no lipid at all up to 32 mM. All the dihydroxy bile acids are much more efficient at solubilizing phospholipid than cholesterol. Cholate does not show such a pronounced discrimination. Lipid solubilization by chenodeoxycholate was essentially complete within 1 min, whereas that by cholate was linear up to 5 min. Maximal lipid solubilization with chenodeoxycholate occurred at 8-12 mM; solubilization by cholate was linear up to 32 mM. Ursodeoxycholate was the only dihydroxy bile salt which was able to solubilize phospholipid (although not cholesterol) below the critical micellar concentration. This similarity between cholate and ursodeoxycholate may reflect their ability to form a more extensive liquid-crystal system. Membrane specificity was demonstrated only inasmuch as the lower the cholesterol/phospholipid ratio in the membrane, the greater the fractional solubilization of cholesterol by bile salts, i.e. the total amount of cholesterol solubilized depended only on the bile-salt concentration. On the other hand, the total amount of phospholipid solubilized decreased with increasing cholesterol/phospholipid ratio in the membrane.

Animals↗
PubMed1996

The functional expression of sodium-dependent bile acid transport in Madin-Darby canine kidney cells transfected with the cDNA for microsomal epoxide hydrolase.

Previous studies have suggested that the enzyme microsomal epoxide hydrolase (mEH) is able to mediate sodium-dependent transport of bile acids such as taurocholate into hepatocytes (von Dippe, P., Amoui, M., Alves, C., and Levy, D.(1993) Am. J. Physiol. 264, G528-G534). In order to characterize directly the putative transport properties of the enzyme, a pCB6 vector containing the cDNA for this protein (pCB6-mEH) was transfected into Madin-Darby canine kidney (MDCK) cells, and stable transformants were isolated that could express mEH at levels comparable with the levels expressed in hepatocytes. Sodium-dependent transport of taurocholate was shown to be dependent on the expression of mEH and to be inhibited by the bile acid transport inhibitor 4,4'-diisothiocyanostilbene-2,2'disulfonic acid (DIDS), as well as by other bile acids. Kinetic analysis of this system indicated a Km of 26.3 microM and a Vmax of 117 pmol/mg protein/min. The Km value is essentially the same as that observed in intact hepatocytes. The transfected MDCK cells also exhibited sodium-dependent transport of cholate at levels 150% of taurocholate in contrast to hepatocytes where cholate transport is only 30% of taurocholate levels, suggesting that total hepatocyte bile acid transport is a function of multiple transport systems with different substrate specificities, where mEH preferentially transports cholate. This hypothesis is further supported by the observation that a monoclonal antibody that partially protects (26%) taurocholate transport from inhibition by DIDS in hepatocytes provides almost complete protection (88%) from DIDS inhibition of hepatocyte cholate transport, suggesting that taurocholate is also taken up by an alternative system not recognized by this antibody. Additional support for this concept is provided by the observation that the taurocholate transport system is almost completely protected (92%) from DIDS inhibition by this antibody in MDCK cells that express mEH as the only bile acid transporter. These results demonstrate that mEH is expressed on the surface of hepatocytes as well as on transfected MDCK cells and is able to mediate sodium-dependent transport of taurocholate and cholate.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1953

Observations concerning the production and excretion of cholesterol in mammals. IX. The mechanism of the hypercholesteremic effect of cholic acid.

Accumulation of cholate in plasma is the immediate cause of hypercholesteremia in the rat with bile duct ligation and in the normal rat given intravenous sodium cholate. The hypercholesteremia induced by cholate administration does not appear to be dependent upon any preceding change in the rates of absorption, excretion, synthesis, or redistribution of cholesterol in the tissues of the animal. Cholate administration seems to induce hypercholesteremia by impeding the normal rate of passage of cholesterol from the plasma into the liver; this impedance is probably due to an alteration of the cholesterol-binding power of plasma proteins induced by cholate. The chemical and physiological implications of this finding are discussed.

Animals↗
PubMed1985

Studies on the interaction of Clostridium perfringens sialidase with sialic acid linked to the internal galactose in monosialogangliotetraosyl ceramide.

Investigation of the action of highly purified Clostridium perfringens sialidase on ganglioside II3Neu5Ac-Gg4Cer and its oligosaccharide II3Neu5Ac-Gg4, in the presence and absence of sodium cholate, extend earlier results obtained with impure enzyme fractions. Sialidase labeled with 125I was found to bind to various ganglioside substrate micelles, including II3Neu5Ac-Gg4Cer, and to mixed ganglioside-sodium cholate micelles. No binding occurred between the enzyme and the ganglioside-derived oligosaccharide II3Neu5Ac-Gg4, even when radioactive II3Neu5Ac-Gg4-[3H]ol was used. The binding of sialidase to micellar substrate is a condition for enzymic hydrolysis. Correspondingly, II3Neu5Ac-Gg4Cer and II3Neu5Ac-Gg4Cer-sodium cholate micelles were hydrolyzed by the enzyme but II3Neu5Ac-Gg4 was not. Ganglioside oligosaccharide analogues containing an amino function at the reducing terminus or between two oligosaccharide chains, II3Neu5Ac-Gg4-NH2 and (II3Neu5Ac-Gg4)2NH, were hydrolyzed in the absence of cholate. A synthetic analogue of II3Neu5Ac-Gg4Cer containing only the fatty acid moiety and not the sphingosine residue (I1-deoxy-I1-stearamido-II3-monosialo-gangliotetraitol ) behaved as the ganglioside in the presence and absence of sodium cholate.

Chemical Phenomena↗
PubMed1982

Studies on the reconstitution of o(2)-evolution of chloroplasts.

Extraction of spinach (Spinacia oleracea L.) chloroplasts with cholate-asolectin in the absence of Mg(2+) results in the rapid and selective inactivation of O(2) evolution and a partial (30 to 40%) loss of photosystem II (PSII) donor activity without extraction of thylakoid bound Mn ( approximately 5 to 6 Mn per 400 Chlorophyll). Inclusion of ethylene glycol in the extractions inhibits loss of O(2) evolution and results in quantitative and qualitative differences in proteins solubilized but does not significantly inhibit the partial loss of PSII donor activity. Similarly, in two stage experiments (extraction followed by addition of organic solvent and solubilized thylakoid protein), O(2) evolution (V and V(max)) of extracted chloroplasts is enhanced approximately 2.5- to 8-fold. However, PSII donor activity remains unaffected. This reversal of cholate inactivation of O(2) evolution can be induced by solvents including ethanol, methanol, 2-propanol, and dimethyl sulfoxide. Such enhancements of O(2) evolution specifically required cholate-solubilized proteins, which are insensitive to NH(2)OH and are only moderately heat-labile. NH(2)OH extraction of chloroplasts prior to cholate-asolectin extraction abolishes reconstitutability of O(2) evolution. Thus, the protein(s) affecting reconstitution is unlike those of the O(2).Mn enzyme. The specific activity of the protein fraction effecting reconstitution of O(2) evolution is greatest in fractions depleted of the reported Mn-containing, 65-kilodalton, and the Fe-heme, 232-kilodalton (58-kilodalton monomer), proteins. Divalent ( approximately 3 millimolar) and monovalent ( approximately 30 millimolar) cations do not affect reconstitution of PSII donor activity but do affect reconstitution of O(2) evolution by decreasing the protein(s) concentration required for reconstitution of O(2) evolution in nonfractionated, cholate-asolectin extractions. The data indicate a reconstitution of the PSII segment linking the PSII secondary donor(s) to O(2)-evolving centers.

Journal Article↗
PubMed1972

Murein and the outer penetration barrier of Escherichia coli K-12, Proteus mirabilis, and Pseudomonas aeruginosa.

A penetration barrier operating outside the periplasmic enzyme penicillinase was studied in an ampicillin-resistant mutant of Escherichia coli K-12. Growth in the presence of lysozyme and sublethal concentrations of ampicillin partially opened the barrier. This could be recorded as an increased penetration of penicillin G, sodium cholate, and rifampin to their respective targets. Brief treatments with tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid and sodium cholate effectively impaired the barrier against penicillin and also caused leakage of penicillinase. Wild-type E. coli K-12, Proteus mirabilis, and Pseudomonas aeruginosa also showed an increased sensitivity to cholate after treatment with penicillins. Electron micrographs showed that lysis by cholate was due to a distortion of the cytoplasmic membrane causing a leakage of protein and RNA from the cells to the medium. Physiological data indicated that the increased sensitivity to cholate induced by growth in the presence of ampicillin or lysozyme was due to effects upon the murein. This was supported by measurement of the incorporation of (3)H-diaminopimelic acid. These results indicate that the murein sacculus either is a part of the penetration barrier or is responsible for holding the structure of the outer membrane together.

Ampicillin↗
PubMed1970

Morphological changes of the small-intestinal mucosa of guinea pig and hamster following incubation in vitro and perfusion in vivo with unconjugated bile salts.

Incubation in vitro of the intestine of the hamster and guinea pig with 5 mM sodium cholate and with 2 mM sodium deoxycholate and sodium chenodeoxycholate resulted in significant morphological changes compared with control incubations. Generally, no major differences were observed between proximal and distal small intestine or between the species used. Only when guinea pig intestine was incubated with 5 mM cholate was less damage found proximally than distally. Perfusion in vivo of the intestine of the hamster and guinea pig with Krebs-Ringer phosphate results in separation of the epithelium from the lamina propria without excessive shedding of epithelial cells from villous tips. This change was also seen in specimens taken before perfusion and probably represents unavoidable trauma during handling of the intestine. In contrast to studies in vitro, regional differences are readily demonstrable with perfusion of bile salts in vivo. Dihydroxy bile salts produce more marked alterations of both proximal and distal small intestine than the trihydroxy bile salt, sodium cholate. Dihydroxy bile salts result in significantly greater alterations in proximal than in distal mucosa. When 5 mM cholate at pH 6.8 is perfused in the guinea pig, absorption occurs approximately 30 times more rapidly from distal than from proximal segments, while in proximal segments 2 mM chenodeoxycholate is absorbed approximately 15 times more rapidly than 5 mM cholate. A correlation is suggested between the morphological alteration produced in the region of the small intestine by a bile acid and the amount of bile salt passing through the cell. Furthermore, it is proposed that the ileal cells may be damaged to a lesser extent by bile acids normally found in that particular species.

Animals↗
PubMed1981

Clinical value of bile salt tests in anicteric liver disease.

Fasting and postprandial serum bile salt concentrations and intravenous glycocholate disappearance were studied in 20 patients with anicteric liver disease who had only minor abnormalities of conventional liver function tests. Abnormalities in the fasting or two hour postprandial conjugated cholate concentrations were found in all but one of the patients who had an abnormality in bilirubin concentration. In these patients, fasting and postprandial conjugated cholate concentrations were raised on average three and two times respectively above the upper limit of the reference range, while bilirubin concentration was raised only 50%. Postprandial conjugated cholate concentrations were also abnormal in two patients with normal bilirubin concentrations. Measurement of fasting and postprandial conjugated chenodeoxycholate concentration and intravenous glycocholate disappearance proved less informative than the fasting and postprandial conjugated cholate test. These results suggest that, where bilirubin concentrations are normal or only slightly raised, measurement of serum fasting and two hour postprandial conjugated cholate concentrations may prove helpful in the detection of minor abnormalities in hepatic anion transport.

Adult↗
PubMed1986

Structural characterization of cholylcoenzyme A:glycine-taurine N-acyltransferase and a covalent substrate intermediate.

Bile acid-CoA:glycine-taurine N-acyltransferase was found to catalyze a reaction in the absence of glycine or taurine in which the substrate cholyl-CoA is cleaved with the release of CoA and the formation of a covalently bound enzyme-cholate intermediate. This unstable intermediate was trapped by a rapid mixing and denaturation procedure. The denatured protein was digested with trypsin and the cholate-labeled tryptic peptide was isolated. This cholate-peptide is considered to originate from the active site region of the enzyme based on the following criteria: cholyl-CoA does not react with any of the 20 common amino acids, the hydrolysis of cholyl-CoA is known to occur on the enzyme, the lack of reaction of the enzyme with just cholate, and the fact that labeling is extensive even at low (substrate level) concentrations of cholyl-CoA. The isolated cholate-peptide was submitted to amino acid analysis. It contained 32 amino acid residues and was devoid of cysteine, methionine, and tyrosine. Amino acid analysis of the N-acyltransferase was conducted. The enzyme was also shown to possess a blocked N terminus.

Acyltransferases↗
PubMed1981

Hysteretic activation of adenylyl cyclases. II. Mg ion regulation of the activation of the regulatory component as analyzed by reconstitution.

The rate of appearance and extent of reconstituted adenylyl cyclase activity in the presence of guanyl-5'-yl imidodiphosphate (GMP-P(NH)P) upon mixing cholate extract of rat liver 10,000 X g particulate preparation and S49 cyc- cell membranes was dependent on Mg ion concentration. Increasing concentrations of Mg ion lead to progressively shorter lag times in the appearance of reconstituted activity. In contrast, at 20 mM MgCl2, the rate of appearance of reconstituted activity was insensitive to concentrations of GMP-P(NH)P, cyc- membrane protein, and untreated cholate extract protein, but became sensitive to cholate extract protein concentration after treatment with GMP-P(NH)P and Mg ion. Treatment of cholate extract with GMP-P(NH)P and Mg ion resulted in a faster appearance of reconstituted activity upon exposure to S49 cyc- membranes as compared to treatment in the presence of GMP-P(NH)P and EDTA. Activation of the regulatory component by GMP-P(NH)P occurred only in the presence of Mg ion. Mn2+, Ca2+, or Ba2+ did not appear to substitute for Mg. The effect of Mg ion allowing for the rapid appearance of reconstituted activity was reversible in the presence or absence of S49 cyc- membranes. However, while dilution of GMP-P(NH)P in the absence of S49 cyc- membranes resulted in relatively rapid reversal, treatment of cholate extract with 5 microM GMP-P(NH)P and 20 mM Mg ion followed by reconstitution at 5 or 0.1 microM GMP-P(NH)P showed similar reconstituted activities for up to 15 min. The rate of activation of the regulatory component was faster at 20 mM Mg ion as compared to that at 1 mM Mg ion. Similarly, the rate of activation of the regulatory component by NaF was also accelerated by increasing the concentration of Mg ion. These data indicate that the rate-limiting step in the activation of adenylyl cyclase is conversion of the regulatory component from its inactive to active form. In the presence of saturating concentration of guanine nucleotides and NaF, both the rate and extent of this activation is regulated by Mg ion.

Adenylyl Cyclases↗
PubMed1994

Immortalization of rat hepatocytes by fusion with hepatoma cells. II. Studies on the transport and synthesis of bile acids in hepatocytoma (HPCT) cells.

Hepatocytoma (HPCT) cells were screened for the uptake of bile acids, the organic anion bumetanide and phalloidin. In addition, the rate of bile acid synthesis and the ability to conjugate exogenously added free bile acids was investigated. The unconjugated bile acid cholate is transported via carrier-mediated uptake into HPCT cells of the clone 1E3. This transport is expressed less by HPCT clones 1F9 and 2E9. Cholate uptake is 40% sodium-dependent, temperature-sensitive, and reveals a km-value of 47 +/- 9 pmol/l and a Vmax-value of 94 +/- 29 pmol x min-1 x mg-1. However, all of the HPCT clones lack carrier-mediated uptake of glycocholate and taurocholate. The clones which possess cholate transport are sensitive to phalloidin and take up bumetanide. In higher cell passages cholate transport and the sensitivity to phalloidin are reduced. This process is not prevented by a selection procedure with HAT-medium, nor is it stimulated by nicotinamide, dimethyl sulfoxide, or sodium butyrate. The cells of the 1E3, 1F9 and 2E9 clones, but not Fao hepatoma cells synthesize bile acids endogenously even after 60 passages, and conjugate exogenously added cholate with taurine and glycine. These results indicate that liver-specific properties of freshly isolated hepatocytes which are lacking in the parental hepatoma cells are maintained in HPCT cells.

Animals↗
PubMed2000

Oestradiol skin delivery from ultradeformable liposomes: refinement of surfactant concentration.

The aims of this study were to refine ultradeformable liposomes for oestradiol skin delivery and to evaluate Span 80 and Tween 80 as edge activators compared with sodium cholate. Vesicles containing phosphatidylcholine (PC) mixed with edge activators and oestradiol were prepared. Entrapment efficiency and vesicle size were determined. Interactions between activators and vesicles were investigated using differential scanning calorimetry. Transepidermal permeation of oestradiol from vesicles was studied compared to saturated aqueous control in vitro. The maximum flux (J(max)) and its time (T(max)) were calculated from the flux curves and skin deposition was assessed. The compositions of refined formulations were predicted, liposomes prepared, and tested against control. Entrapment efficiency depended on PC concentration with some contribution from sodium cholate and Tween 80. Vesicle sizes ranged from 124 to 135 nm. Edge activators interacted with lipid bilayers and disrupted packing. The refined edge activator concentrations in PC vesicles were 14.0, 13.3 and 15.5% w/w for sodium cholate, Span 80 and Tween 80, respectively; they increased J(max) by 18, 16 and 15-fold and skin deposition by 8, 7 and 8-fold compared with control. Ultradeformable vesicles thus improved skin delivery of oestradiol compared to control and Span 80 and Tween 80 were equivalent to sodium cholate as edge-activators.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

Cooperativity and oligomeric status of cardiac muscarinic cholinergic receptors.

Muscarinic cholinergic receptors can appear to be more numerous when labeled by [(3)H]quinuclidinylbenzilate (QNB) than by N-[(3)H]methylscopolamine (NMS). The nature of the implied heterogeneity has been studied with M(2) receptors in detergent-solubilized extracts of porcine atria. The relative capacity for [(3)H]NMS and [(3)H]QNB was about 1 in digitonin-cholate, 0.56 in cholate-NaCl, and 0.44 in Lubrol-PX. Adding digitonin to extracts in cholate-NaCl increased the absolute capacity for both radioligands, and the relative capacity increased to near 1. The latency cannot be attributed to a chemically impure radioligand, instability of the receptor, an irreversible effect of NMS, or a failure to reach equilibrium. Binding at near-saturating concentrations of [(3)H]QNB in cholate-NaCl or Lubrol-PX was blocked fully by unlabeled NMS, which therefore appeared to inhibit noncompetitively at sites inaccessible to radiolabeled NMS. Such an effect is inconsistent with the notion of functionally distinct, noninterconverting, and mutually independent sites. Both the noncompetitive effect of NMS on [(3)H]QNB and the shortfall in capacity for [(3)H]NMS can be described quantitatively in terms of cooperative interactions within a receptor that is at least tetravalent; no comparable agreement is possible with a receptor that is only di- or trivalent. The M(2) muscarinic receptor therefore appears to comprise at least four interacting sites, presumably within a tetramer or larger array, and ligands appear to bind in a cooperative manner under at least some conditions.

Animals↗
PubMed2003

Effect of mixed micelle formulations including terpenes on the transdermal delivery of diclofenac.

The significant inhibitory action of diclofenac formulated in mixed micelles of lecithin with cholate or deoxycholate was observed on the rat hind paw edema induced by carrageenan. In the primary stage, mixed micelle formulation of deoxycholate was more effective compared with that of cholate. However, in the final term, the inhibitory action was similar in both formulations. In a previous study, the flux of diclofenac was greater in the mixed micelle formulation of deoxycholate compared with that of cholate. It was suggested that the permeation rate of diclofenac through skin was proportional to the pharmacological activity. The hind paw edema was quickly inhibited when cyclic monoterpene such as d-limonene or l-menthol was included in the formulations. All the micelle formulations significantly decreased the value of AUC estimated the hind paw thickness-time profile. This suggests that the micelle formulation of cholate in addition to deoxycholate showed significant anti-inflammatory activity to hind paw edema of rats. Incorporation of d-limonene or l-menthol was more effective on the decrease of AUC. A pharmacological study revealed that micelle formulations were able to reduce the skin irritation of chemicals.

Administration, Cutaneous↗
PubMedDate not supplied

Accumulation of vinblastine into transfersomes and liposomes in response to a transmembrane ammonium sulfate gradient and their cytotoxic/cytostatic activity in vitro.

Vinblastine was encapsulated into liposomes composed from lipids dimiristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC), with cholesterol and transfersomes with sodium cholate prepared by the thin film hydration method. The percentage of vinblastine encapsulation, the stability of transfersomes and liposomes and the rate of release of encapsulated vinblastine at 37 degrees C were studied. The results showed that encapsulation of vinblastine into liposomes was higher than 98% at a drug/phospholipid molar ratio from 0.17 to 0.18, while encapsulation of vinblastine into transfersomes varied from 50% to 80% at a drug/phospholipid molar ratio from 0.05 to 0.09. The retention of drug in liposomes and in transfersomes was found to be time/dependent. The retention of drug in transfersomes compared to the liposomes was reduced due to the presence of sodium cholate which caused destabilization and reduced the main phase transition temperature Tm of the PC bilayers. The cytotoxic/cytostatic activity of the two liposome formulations and the two transfersome formulations with or without encapsulated vinblastine were examined against nine human cell lines and the parameters GI50, TGI, LC50 were estimated according to the NCI protocol. Free DPPC/sodium cholate liposomes found to exhibit strong antiproliferative activity in contrast to the other three free liposomal formulations (DPPC/cholesterol, DMPC/cholesterol, DMPC/sodium cholate). On the other hand, vinblastine encapsulated into the liposomes found to exhibit 20-fold less activity on average, in the three parameters calculate compare to the free vinblastine.

1,2-Dipalmitoylphosphatidylcholine↗