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PubMed1999

Modulation of glycinergic synaptic current kinetics by octanol in mouse hypoglossal motoneurons.

Octanol-induced changes in the kinetics of glycinergic inhibitory postsynaptic currents (IPSCs) were investigated by whole-cell recording from hypoglossal motoneurons in mouse brainstem slices. Octanol (1 mM) prolonged the decay time constants (tau(decay)) of stimulus-evoked IPSCs (e-IPSCs) by 202+/-67% (SE). The depression of e-IPSC amplitudes was dose-dependent with an EC50 of 475 microM. Octanol also reduced the amplitude and prolonged the decay time constant of glycinergic currents evoked by local pressure ejection of glycine (I(gly)). Replacement of extracellular Na+ by choline and application of the specific glycine transporter GLYT1 inhibitor, sarcosine, lengthened tau(decay) of I(gly), but did not change the decay time constants of e-IPSCs. Intracellular acidification by the weak organic acid salt sodium propionate (30 mM) reduced the e-IPSC amplitude by 22+/-9% and prolonged tau by 18+/-6%. Sodium propionate also prolonged the decay time constants of I(gly) by 28+/-11%. The observed effects on decay kinetics were much smaller than those caused by octanol. The data show that octanol prolongs the decay time course of glycinergic synaptic currents by mechanisms independent of glycine uptake or intracellular acidification. We conclude that the effects were most probably due to direct action on postsynaptic glycine receptors.

Amino Acid Transport Systems, Neutral↗
PubMed1979

The interaction of n-octanol with black lipid bilayer membranes.

The electrical capacities of black lipid films formed from monoolein + n-hexadecane and monoolein + squalane (or squalene) solutions have been measured in the presence of various concentrations of n-octanol. In addition, partition coefficients for n-octanol between n-hexadecane and 0.1 M NaCl, dielectric constants for octanol-hexadecane mixtures and the interfacial tension of films and film-forming lipid solutions against the aqueous phases have been determined. It is concluded that in "solvent-free" bilayers the octanol is unlikely to have changed the bilayer thickness by more than about 1 A. The bilayer tension, on the other hand, increases appreciably in the presence of octanol.

Electrochemistry↗
PubMed1988

Assessment of the arterial input curve for [99mTc]-d,l-HM-PAO by rapid octanol extraction.

The in vitro conversion of the lipophilic molecule [99mTc]-d,l-hexamethylpropyleneamine oxime [( 99mTc]-d,l-HM-PAO) to a hydrophilic form was studied in saline, plasma, and blood at 37 degrees C by paper chromatography and by octanol extraction. The octanol:saline ratio was 79.9. From this value and the corresponding octanol: plasma and octanol:blood partitioning values, an estimate of the transport of the lipophilic compound by various components of blood was made: 20% is carried in hemoglobin, 53% by the plasma proteins and 27% by the water phases of the red blood cell and plasma. Octanol extraction provided a rapid method for measuring the radiochemical purity (RCP) of lipophilic [99mTc]-d,l-HM-PAO. In saline, the RCP declined with a half-life of more than 1 h. In human plasma and whole blood, the conversion of [99mTc]-d,l-HM-PAO was biexponential due to the differences in the conversion rates of the d and l isomeric forms. The initial half-life representing the conversion rate of the l form was 1.7 min in blood and 1.4 min in plasma, while the conversion half-life of the d form was 7.4 and 24.4 min, respectively. In vivo, the RCP of arterial blood sampled after an i.v. bolus injection showed an initial peak value of 75% (68-79%) during the initial, first passage of the bolus. It declined to approximately 35% (29-40%) after 1.5 min and reached very low levels (about 1%) at 6 to 10 min. Quantitative measurements of cerebral blood flow using [99mTc]-d,l-HM-PAO necessitates a rapid method for RCP determination in arterial blood such as the one described here.

Arteries↗
PubMed2004

Octanol modulation of neuronal nicotinic acetylcholine receptor single channels.

BACKGROUND: We have previously shown that alcohols exert a dual action on neuronal nicotinic acetylcholine receptors (AChRs), with short-chain alcohols potentiating and long-chain alcohols inhibiting acetylcholine (ACh)-induced whole-cell currents. At the single-channel level, ethanol increased the channel open probability and prolonged the channel open time and burst duration. In this study, we examined the detailed mechanism of the inhibitory action of the long-chain alcohol n-octanol on the neuronal nicotinic AChR. METHODS: Single-channel currents induced by application of 30 nm ACh were recorded with the patch-clamp technique from human embryonic kidney cells stably expressing the human alpha4beta2 AChR. RESULTS: Several single-channel parameters were markedly changed by octanol. At least two conductance-state currents were induced by low concentrations of ACh, and octanol increased the proportion of the low-conductance-state current relative to the high-conductance-state current without changing the current amplitude. Major analyses of temporal properties of single-channel currents were performed on the high-conductance-state currents. Octanol decreased the burst duration and duration of openings within burst and prolonged the mean closed time. All of these changes contributed to the decrease in the open probability in a concentration-dependent manner. CONCLUSIONS: Several aspects of octanol action on neuronal AChRs at the single-channel level are compatible with an atypical open channel block model reported with muscle nicotinic AChRs. The potentiating action of short-chain alcohols and the inhibitory action of long-chain alcohols on the neuronal nicotinic AChR are mediated through different mechanisms.

Acetylcholine↗
PubMed1988

A novel method for measuring membrane-water partition coefficients of hydrophobic organic chemicals: comparison with 1-octanol-water partitioning.

A novel method of measuring membrane-water partitioning characteristics of very hydrophobic organic chemicals is described. Partition coefficients are reported for a series of halogenated aromatic hydrocarbons of varying molar volume between water and L-a-phosphatidylcholine dimyristoyl (DMPC) membrane vesicles and two solvents, n-hexane and 1-octanol. The results indicate that n-hexane and 1-octanol are satisfactory surrogates for DMPC membranes for chemicals with 1-octanol-water partition coefficients (log KOW) less than 5.5 or molar volumes less than 230 cm3/mol. Chemicals with higher log KOW or molar volume values display marked differences in membrane-water, 1-octanol-water, and n-hexane-water partitioning. Implications for lipid- and organism-water partitioning of hydrophobic chemicals are discussed.

1-Octanol↗
PubMed1995

Enhancement of melphalan toxicity by octanol in ovarian adenocarcinoma cell lines: effects of altered cell-cell communication, glutathione levels, and plasma membrane fluidity.

A2780 and COLO-316 ovarian adenocarcinoma cell lines were exposed to 1.0 mM 1-octanol for 12 hr in order to evaluate the potential effects of inhibition of gap junction-mediated intercellular communication (GJIC) on cellular responses to the chemotherapeutic drug melphalan. Other cellular endpoints relevant to drug-resistance mechanisms which were monitored after treatments included cellular glutathione levels, glutathione S-transferase activity, mitochondrial membrane potential, and plasma membrane lipid mobility. In cells which were sensitive to melphalan, octanol enhanced melphalan toxicity in the GJIC-competent (A2780/S) but not GJIC-incompetent (COLO-316/S) sensitive cells. Although octanol increases plasma membrane lipid mobility in A2780/S and COLO-316/S, it appears that enhancement of A2780/S sensitivity to melphalan may be due to inhibition of GJIC. In melphalan-resistant cells (A2780/R and COLO-316/R), 1.0 mM octanol treatment for 12 hr combined with melphalan reversed the resistance of the cells to the drug. Therefore, alterations in cellular glutathione metabolism and effects on the plasma membrane in addition to uncoupling of GJIC may be involved in sensitizing communication-competent and communication-incompetent resistant cells because COLO-316/R lacks gap junction-mediated intercellular communication. Further, analysis of mitochondrial membrane potential provided an index of acquired drug resistance and the efficacy of melphalan and combined octanol/melphalan toxicity.

1-Octanol↗
PubMed1978

Simple procedure for determining octanol--aqueous partition, distribution, and ionization coefficients by reversed-phase high-pressure liquid chromatography.

The described simple, accurate, and precise reversed-phase high-pressure liquid chromatographic procedure is in excellent agreement with 1-octanol shake-flask partition or distribution coefficients over a 3.5 log range. A chemically bonded octadecylsilane support is persilated and coated with 1-octanol. With 1-octanol-saturated buffers as mobile phases, a stable baseline (compared to 1-octanol adsorbed on silica) is obtained rapidly, and the log relative retention times are highly correlated with unit slope to log distribution or partition coefficients obtained from the classical shake-flask procedures. Only relatively basic, unhindered pyridines deviate, probably because of binding with residual silinol sites. In addition, if the apparent pKa or pKab of an ionizable compound lies within the pH operating range of the column support, the apparent pKa or pKab usually can be determined simultaneously with log P by measuring the log distribution coefficient at several pH values. The procedure gives rapid results, requires little material, and can tolerate impurities.

Chemistry, Pharmaceutical↗
PubMed1995

pH-metric log P. 6. Effects of sodium, potassium, and N-CH3-D-glucamine on the octanol-water partitioning of prostaglandins E1 and E2.

The pH-dependent octanol-water partition behavior of prostaglandins (Pg) E1 and E2 was studied by an automated potentiometric titration method. In 0.15 M KCl at 25 degrees C, the log P values of PgE1 and PgE2 are 3.20 +/- 0.02 and 2.90 +/- 0.02, respectively. The partition parameter also was determined in 0.15 M NaCl, 0.10 M NaCl, and 0.0003 M KCl for PgE1; no ionic strength dependence was observed. In contrast, the Pg anion partitioning, described by the extraction constant, log Ke (= [X+Pg-]OCT/[X+]AQ[Pg-]AQ, where X = Na or K), showed dependence on the nature and concentration of the background salt. For PgE1, the log Ke values are 0.50 +/- 0.08 (0.15 M KCl), 0.18 +/- 0.16 (0.15 M NaCl), 0.86 +/- 0.08 (0.10 M NaCl), and 1.80 +/- 0.09 (0.0003 M KCl); for PgE2, the log Ke value is 0.20 +/- 0.29. The extraction of the Pg anion into octanol by N-methyl-D-glucamine (glucamine) was also studied. In 0.15 M KCl, the log Ke value is 1.82 +/- 0.07. The extraction of the prostaglandin-glucamine complex into octanol maximizes at about pH 8.8. Due to the low aqueous solubility of the prostaglandins, the aqueous pKa values were determined by extrapolation from methanol-water solutions by the Yasuda-Shedlovsky technique. The Debye-Hückel theory was applied to predict the ionic strength dependence of the octanol-water ion-pair extraction constants (log Ke).

Alprostadil↗
PubMedDate not supplied

Speciation analysis and the assessment of bioavailability of manganese in phytomedicines by extraction with octanol and determination by flame atomic absorption spectrometry.

Trace elements in phytomedicines are present in the form of metallic complexes. Since n-octanol, a long-chain alkanol, presents a configuration similar to that of carbohydrates and lipids, the lipophilicity and absorptivity of organic medicines may be assessed from their distribution coefficients between octanol and water. This strategy has been used in order to define the species of manganese in a number of phytomedicines and to study the distribution of manganese in decoctions of phytomedicines in the stomach and the intestine. The concentrations of manganese in the original herbal materials and in octanol- and water-soluble fractions were determined by flame atomic absorption spectrometry following mixed acid digestion. The acidities of gastric and intestinal juices, the phytomedical composition and the compatibility of phytomedicines, i.e. the combination of single phytomedicines, greatly affected the manganese complexing ligands and determined the species and bioavailability of manganese. It is concluded that a knowledge of the level of octanol-soluble manganese in a phytomedicine could form the basis of dosage design in order to avoid manganese overload.

Acids↗
PubMed1993

Distribution of hydrophobic ionizable xenobiotics between water and lipid membranes: pentachlorophenol and pentachlorophenate. A comparison with octanol-water partition.

We have studied distribution of pentachlorophenol (PCP)--a major environmental pollutant--between egg-phosphatidylcholine (egg-PC) membranes and water. The objectives were (1) to compare the membrane-water partition of the un-ionized (HA) and ionized (A) PCP, and (2) to establish similarities and differences between the partition of PCP into lipid membranes and into octanol. The studies were made with egg-PC liposomes. It is shown that the distribution isotherms can be understood in terms of the Langmuir-Stern-Grahame adsorption model. The model is applicable to both the HA and A species; it takes into account the electrostatic interactions at the membrane-water interface charged by the adsorbed pentachlorophenate. Relationships between the membrane surface adsorption and bulk partition characteristics were presented and used to relate the partition of PCP into egg-PC membranes to those for octanol-water systems. Results (egg-PC membranes): bulk distribution coeff. gamma HA = 2.9 x 10(5), gamma A = 1.6 x 10(4), association constant KmHA = 2.9 x 10(5) M-1, KmA = 0.7 x 10(5) M-1, adsorption site area PsHA = 0.6 nm2, PsA = 3.5 nm2, and linear partition coeff. Beta mHA = 550 microns, beta mA = 30 microns. Comparable to gamma HA and gamma A for octanol-water are P(ow)(HA) approximately 1.3 x 10(5) and P(ow)(A) approximately 30. The major difference is in the distribution of ionized PCP which is several hundred times greater for egg-PC membranes compared to octanol. The difference is associated with the properties of the membrane-water interface.

Membranes, Artificial↗
PubMed2006

Determination of n-octanol-water partition coefficients by hollow-fiber membrane solvent microextraction coupled with HPLC.

A novel direct method has been developed for determination of n-octanol-water partition coefficients by hollow-fiber membrane solvent microextraction (HFMSME) combined with high-performance liquid chromatography (HPLC). The compound of interest is dissolved in water with sonication and a hollow fiber containing octanol inside is placed in the sample solution to perform microextraction. After microextraction the concentrations in both the aqueous and n-octanol phases are analyzed by HPLC with UV detection. The method was evaluated with ten reference compounds and shown to be suitable for determination of the partition coefficients of organic compounds accurately, cheaply, simply, and quickly. Previously unknown n-octanol-water partition coefficients have been obtained for other compounds by use of the hollow-fiber membrane solvent-microextraction technique.

1-Octanol↗
PubMed1995

Determination of true octanol-water partition coefficients by means of solvent generated liquid-liquid chromatography.

Compared to other methods for the determination of octanol-water partition coefficients chromatography offers a number of advantages: sample purification is unnecessary, the partition coefficients of the components of a mixture can be measured simultaneously and a minimum amount of sample is needed. In the past these determinations were almost exclusively carried out by liquid-solid chromatography (LSC) on alkyl bonded silica as stationary phase (conventionally described as 'reversed-phase liquid chromatography; RPLC). Such systems based on liquid-solid distribution are, however, a poor simulation of liquid-liquid partition. On the other hand liquid-liquid chromatographic columns loaded with high amounts of water-saturated octanol are unstable since they suffer from "column bleeding"--a loss of the stationary liquid octanol phase caused by erosion. It is shown that the technique of solvent generated liquid-liquid chromatography (SGLLC) leads to stable columns with liquid-liquid partition as the predominant retention mechanism, if systematic errors due to specific adsorption effects are avoided by the selection of an "inert" solid support. This is demonstrated by the comparison of LSC and SGLLC data. SGLLC significantly reduces the scattering of the retention data of calibration standards around the calibration line. The use of SGLLC thus significantly improves the accuracy and precision of the resulting octanol-water partition coefficients.

Adsorption↗
PubMed2002

Rapid estimation of octanol-water partition coefficients using synthesized vesicles in electrokinetic chromatography.

Vesicle electrokinetic chromatography (VEKC) using vesicles synthesized from the oppositely charged surfactants cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) and from the double-chained anionic surfactant bis(2-ethylhexyl)sodium sulfosuccinate (AOT) was applied to the indirect measurement of octanol-water partition coefficients (log Po/w). A variety of small organic molecules with varying functional groups, pesticides, and organic acids were evaluated by correlating log Po/w and the logarithm of the retention factor (log k') and comparing the calibrations. A linear solvation energy relationship (LSER) analysis was conducted to describe the retention behavior of the vesicle systems and compared to that of octanol-water partitioning. The solute hydrogen bond donating behavior is slightly different with the vesicle interactions using CTAB-SOS vesicles as compared to the octanol-water partitioning model. The AOT vesicle and octanol-water partitioning systems showed similar partitioning characteristics. VEKC provides rapid separations for determinations of log Po/w in the range of 0.5 to 5 using CTAB-SOS vesicles and 0 to 5.5 using AOT vesicles.

Cetrimonium↗
PubMed2002

Structures of neat and hydrated 1-octanol from computer simulations.

Molecular dynamics computer simulations of 1-octanol and its mixtures with water have been performed. The liquid is composed of regions enriched in either hydrocarbons or hydroxyl groups. In neat octanol, the hydroxyl groups form clusters of long, thin chains. Upon the addition of water, the clusters become longer and more spherical, forming a structure that can be described as consisting of "overlapping elongated inverse micelles". The structures of the mixtures obtained at different hydration levels are consistent with those of experimental diffraction studies of water/octanol mixtures and previous computer simulations of neat and water-saturated octanol. The saturation point of the model has been calculated using the cavity-bias particle insertion method. The solubility of water in octanol is slightly too low compared to experimental results, and suggestions for possible improvements to the force field are made.

1-Octanol↗
PubMed1998

The hydrophobic effect. 3. A key ingredient in predicting n-octanol-water partition coefficients.

The quantitative development of the mobile order theory in H-bonded liquids is extended to predict the n-octanol/water partition coefficient (P). The log P predictive equation strictly issued from a thermodynamic treatment reduces to a simple linear volume-log P relationship whose intercept and slope encode, respectively, the solvation and entropy effects. For noncomplexing substances, the partition coefficient values result from two volume-dependent entropic contributions reflecting (a) the difference in the exchange entropy between the solute and solvent molecules in the n-octanol and water phases, and (b) the propensity difference between the two H-bonded solvents to induce a hydrophobic effect toward the solute. Although both effects increase, although with opposite signs, compared with the growing molar volume of the partitioned compound, the hydrophobic contribution always predominates favoring the transfer of the solute into the organic phase and hence increasing its partition coefficient. When dealing with complexing chemicals, the hydrophobic effect-related term, though remaining the dominant factor in most cases, is more or less counterbalanced by the formation of H-bonds between the interacting sites of the solute and the n-octanol and water solvent molecules. The log P, corrected for the substantial content of water into n-octanol, is estimated for a number of compounds of environmental and pharmaceutical interest. The extent to which the entropic and enthalpic factors affect the overall partition coefficient value is analyzed.

Chemical Phenomena↗
PubMed2004

Pilot trial of 1-octanol in essential tremor.

1-Octanol (an 8-C alcohol currently used as a food-flavoring agent) is known to inhibit tremor in essential tremor (ET) animal models at a much lower dose than ethyl alcohol. The authors conducted a randomized, placebo-controlled pilot trial of a single oral dose of 1 mg/kg of 1-octanol in 12 patients with ET. No significant side effects or signs of intoxication were observed. 1-Octanol significantly decreased tremor amplitude for up to 90 minutes. The results suggest 1-octanol as a well-tolerated and safe potential treatment for ET. Further trials are warranted.

1-Octanol↗
PubMed2002

Using measured octanol-air partition coefficients to explain environmental partitioning of organochlorine pesticides.

Octanol-air partition coefficients (Koa) were measured directly for 19 organochlorine (OC) pesticides over the temperature range of 5 to 35 degrees C. Values of log Koa at 25 degrees C ranged over three orders of magnitude, from 7.4 for hexachlorobenzene to 10.1 for 1,1-dichloro-2,2-bis(p-chlorophenyl) ethane. Measured values were compared to values calculated as KowRT/H (where R is the ideal gas constant [8.314 J mol(-1) K(-1)], T is absolute temperature, and H is Henry's law constant) were, in general, larger. Discrepancies of up to three orders of magnitude were observed, highlighting the need for direct measurements of Koa. Plots of Koa versus inverse absolute temperature exhibited a log-linear correlation. Enthalpies of phase transition between octanol and air (deltaHoa) were determined from the temperature slopes and were in the range of 56 to 105 kJ mol(-1) K(-1). Activity coefficients in octanol (gamma(o)) were determined from Koa and reported supercooled liquid vapor pressures (pL(o)), and these were in the range of 0.3 to 12, indicating near-ideal solution behavior. Differences in Koa values for structural isomers of hexachlorocyclohexane were also explored. A Koa-based model was described for predicting the partitioning of OC pesticides to aerosols and used to calculate particulate fractions at 25 and -10 degrees C. The model also agreed well with experimental results for several OC pesticides that were equilibrated with urban aerosols in the laboratory. A log-log regression of the particle-gas partition coefficient versus Koa had a slope near unity, indicating that octanol is a good surrogate for the aerosol organic matter.

Aerosols↗
PubMedDate not supplied

[Octanol oxidation by the mitochondria of Torulopsis candida].

Octanol oxidation by the mitochondria of Torulopsis candida grown on hexadecane was studied. Octanol oxidation involves an enzyme system labile to heating but resistant to the main inhibitors of the phosphorylating respiration chain. When octanol is oxidized in aerobic conditions, cytochrome b is reduced, with the absorption maxima in alpha, beta and gamma bands being at 555, 526 and 425 nm, respectively. The cytochrome is reduced in aerobic conditions also in the presence of exogenous NADH and rotenone. In contrast to octanol oxidation, oxidation of the aldehyde C9 by mitochondria was sensitive to the action of inhibitors of the respiration chain and phosphorylation. When the aldehyde C9 is oxidized, cytochrome b is reduced, with the absorption maxima in alpha, beta and gamma bands being at 562, 530 and 433 nm, respectively. The results are indicative of the fact that different electron transport chains are involved in the transport of reducing equivalents from higher alcohols and aldehydes oxidized by mitochondria: in the first case, the NADH--cytochrome b5 reductase chain, and in the second case, the main phosphorylating electron transport chain.

Aerobiosis↗