Neutral amino acid transport by marine fish intestine: role of the side chain

This work was devoted to the study of the structure-affinity relationships in neutral amino acid transport by intestinal brush border of marine fish (Dicentrarchus labrax). The effects of the length of the side chain on kinetics of glycine, alanine, methionine and amino isobutyric acid were investigated. In the presence of K⁺ two components were characterized: one is saturable by increased substrate concentrations, whereas the other can be described by simple diffusion mechanism. Simple diffusion, a passive, non-saturable, Na⁺-independent route, contributes largely to the transport of methionine and to a much lesser extend to alanine, glycine or alphaaminoisobutyric acid uptakes. If a branched chain is present, as in the case of amino isobutyric acid, diffusion is low. A Na⁺-independent, saturable system has been fully characterized for methionine, but not for branched amino acids such as amino isobutyric acid. In the presence of Na⁺ saturable components were shown. Two distinct Na⁺-dependent pathways have been characterized for glycine uptake, with low and high affinities. For alanine and methionine only one Na⁺-dependent high affinity system exists with the same half-saturation concentration and the same maximum uptake at saturable concentrations. Glycine high affinity system has the same half-saturation concentration as methionine or alanine uptake, whereas maximum uptake is lower. The substitution of the hydrogen by a methyl group results in a severe decrease of uptake (aminoisobutyric acid). Mutual inhibition experiments indicate that the same carriers could be responsible for methionine and alanine uptakes and probably glycine Na⁺-dependent uptake. The influence of Na⁺ concentrations (100^-1 mol·l^-1) on amino acid uptake was examined. Glycine, alanine, methionine and amino isobutyric acid transport can be described by a hyperbolic function, with a saturation uptake which is highly increased for methionine. However, the half-saturation concentration does not seem to be strongly affected by the amino acid structure. The effect of Na⁺ concentration (25 and 100 mmol·l^-1) on the kinetics of methionine uptake have been also examined. The maximum uptake of the saturable system clearly shows a typical relationship with concentration.Abbreviations [AA] amino acid concentration - AIB aminoisobutyric acid - [I] Inhibitor amino acid concentration - J _i uptake in the presence of inhibitor - J _o uptake without inhibitor - K _d passive diffusion constant - K _i inhibitor constant - K _t concentration of test amino acid for half-maximal flux - MES 2[N-morpholino]ethanesulphonic acid - V _max maximum uptake at saturable amino acid concentrations - V _tot total amino acid uptake     

Discrimination of competent Bacillus subtilis with respect to ribonucleic acids

Summary A study has been made of the affinity of double-stranded heliced RNA for DNA receptors in competent Bacillus subtilis. In competition experiments, using homologous and heterologous DNA samples which had been sheared to molecular weights comparable to that of the RNA (about 2×10⁶), and which still exhibited appreciable competition in DNA uptake experiments, the replicative form of phage f2 RNA showed no evidence of affinity for receptor sites. A second double-stranded RNA preparation from a widely different source, a mycophage of Penicillium chrysogenum, behaved similarly to the f2 RNA. Transfer RNA and 23S ribosomal RNA, which reduce transformation frequencies in pneumococcus, did not compete for B. subtilis receptors. Lack of competition was not due to enzymatic degradation of the RNA, since the latter was recovered intact following exposure to competent cells. Under conditions where homologous native DNA undergoes normal uptake, there was virtually no uptake of native double-stranded RNA. The results are examined in the light of reports on transformation by RNA and DNA-RNA hybrids, and also in relation to the characterization of the specificity of cell-nucleic acid interactions.     

Optimization of DNA delivery by three classes of hybrid nanoparticle/DNA complexes

Plasmid DNA encoding a luciferase reporter gene was complexed with each of six different hybrid nanoparticles (NPs) synthesized from mixtures of poly (D, L-lactide-co-glycolide acid) (PLGA 50:50) and the cationic lipids DOTAP (1, 2-Dioleoyl-3-Trimethyammonium-Propane) or DC-Chol {3β-[N-(N', N'-Dimethylaminoethane)-carbamyl] Cholesterol}. Particles were 100-400 nm in diameter and the resulting complexes had DNA adsorbed on the surface (out), encapsulated (in), or DNA adsorbed and encapsulated (both). A luciferase reporter assay was used to quantify DNA expression in 293 cells for the uptake of six different NP/DNA complexes. Optimal DNA delivery occurred for 10⁵ cells over a range of 500 ng - 10 μg of NPs containing 20-30 μg DNA per 1 mg of NPs. Uptake of DNA from NP/DNA complexes was found to be 500-600 times as efficient as unbound DNA. Regression analysis was performed and lines were drawn for DNA uptake over a four week interval. NP/DNA complexes with adsorbed NPs (out) showed a large initial uptake followed by a steep slope of DNA decline and large angle of declination; lines from uptake of adsorbed and encapsulated NPs (both) also exhibited a large initial uptake but was followed by a gradual slope of DNA decline and small angle of declination, indicating longer times of luciferase expression in 293 cells. NPs with encapsulated DNA only (in), gave an intermediate activity. The latter two effects were best seen with DOTAP-NPs while the former was best seen with DC-Chol-NPs. These results provide optimal conditions for using different hybrid NP/DNA complexes in vitro and in the future, will be tested in vivo.     

Characterization of DNA uptake by the cyanobacterium Anacystis nidulans

Summary The binding and uptake of nick-translated ³²P-labeled pBR322 by Anacystis nidulans 6301 have been characterized. Both processes were considerably enhanced in permeaplasts compared to cells. The breakdown of labeled DNA was not correlated with binding or uptake by permeaplasts or cells. Uptake of DNA by permeaplasts was unaffected by: Mg²⁺ or Ca²⁺, light, or inhibitors of photophosphorylation such as valinomycin or gramicidin D in the presence or absence of NH₄Cl. ATP at 2.5–10 mM inhibited both binding and uptake of labeled DNA by permeaplasts of A. nidulans whereas the ATP analog adenyl-5-yl imido-diphosphate was non-inhibitory in the same concentration range. In contrast to transformation of A. nidulans 6301 cells to ampicillin-resistance by pBR322, transformation to kanamycin-resistance by the plasmid pHUB4 was considerably enhanced in the dark. The transformation efficiency for permeaplasts by the plasmid pCH1 was 59% and 8% in the dark and light, respectively, whereas transformation of permeaplasts by pBR322 at an efficiency of 16% was absolutely light-dependent.     

Uptake of GABA by neuronal and nonneuronal cells in dispersed cell cultures of postnatal rat cerebellum

A study was made of the time course and kinetics of [³H]GABA uptake by dispersed cell cultures of postnatal rat cerebellum with and without neuronal cells. The properties of GABA neurons were calculated from the biochemical difference between the two types of cultures. It was found that for any given concentration of [³H]GABA, or any time up to 20 min, GABA neurons in cultures 21 days in vitro had an average velocity of uptake several orders of magnitude greater than that of nonneuronal cells. In addition, the apparent K_m values for GABA neurons for high and low affinity uptake were 0.33 × 10⁻⁶ M and 41.8 × 10⁻⁴ M, respectively. For nonneuronal cells, the apparent K_m for high affinity uptake was 0.29 × 10⁻⁶ M. The apparent V_max values for GABA neurons for high and low affinity uptake were 28.7 × 10⁻⁶ mol/g DNA/min and 151.5 mmol/g DNA/min, respectively. For nonneuronal cells, the apparent V_max for high affinity uptake was 0.06 × 10⁻⁶ mol/g DNA/min. No low affinity uptake system for nonneuronal cells could be detected after correcting the data for binding and diffusion. By substituting the apparent kinetic constants in the Michaelis-Menten equation, it was determined that for GABA concentrations of 5 × 10⁻⁹ M to 1 mM or higher over 99% of the GABA should be accumulated by GABA neurons, given equal access of all cells to the label. In addition, high affinity uptake of [³H]GABA by GABA neurons was completely blocked by treatment with 0.2 mM ouabain, whereas that by nonneuronal cells was only slightly decreased. Most (75–85%) of the [³H]GABA (4.4 × 10⁻⁶ M) uptake by both GABA neurons and nonneuronal cells was sodium and temperature dependent.     

Modulation of K+ translocation by AKT1 and AtHAK5 in Arabidopsis plants

Root cells take up K⁺ from the soil solution, and a fraction of the absorbed K⁺ is translocated to the shoot after being loaded into xylem vessels. K⁺ uptake and translocation are spatially separated processes. K⁺ uptake occurs in the cortex and epidermis whereas K⁺ translocation starts at the stele. Both uptake and translocation processes are expected to be linked, but the connection between them is not well characterized. Here, we studied K⁺ uptake and translocation using Rb⁺ as a tracer in wild‐type Arabidopsis thaliana and in T‐DNA insertion mutants in the K⁺ uptake or translocation systems. The relative amount of translocated Rb⁺ to the shoot was positively correlated with net Rb⁺ uptake rates, and the akt1 athak5 T‐DNA mutant plants were more efficient in their allocation of Rb⁺ to shoots. Moreover, a mutation of SKOR and a reduced plant transpiration prevented the full upregulation of AtHAK5 gene expression and Rb⁺ uptake in K⁺‐starved plants. Lastly, Rb⁺ was found to be retrieved from root xylem vessels, with AKT1 playing a significant role in K⁺‐sufficient plants. Overall, our results suggest that K⁺ uptake and translocation are tightly coordinated via signals that regulate the expression of K⁺ transport systems.     

Transplantation of isolated nuclei into plant protoplasts

The uptake of isolated nuclei from Vicia hajastana Grossh. cells into protoplasts of an auxotrophic cell line of Datura innoxia P. Mill. was induced under the influence of polyethylene glycol and Ca²⁺ at pH 6.8. The frequency of nuclear uptake varied from 0.8 to 2.3% and that of the recovery of prototrophic clones from 10^-5 to 6·10^-4. The prototrophic nuclear fusion products following nuclear uptake could be rescued by initial culture of the protoplasts in non-selective conditions and by the subsequent use of feeder cell layers to support the growth of surviving colonies on a selective medium. The presence of Vicia genomic DNA in some prototrophic clones was confirmed by dot-blot hybridization using Datura and Vicia DNA probes. In certain transformed clones, the recovery of prototrophy was accompanied by the restoration of morphogenetic potential. Welldeveloped shoots typical of wild-type Datura could be regenerated employing an appropriate regeneration medium.Abbreviations MS Murashige and Skoog (1962) - PEG polyethylene glycol     

Cytological changes and DNA and protein synthesis in parthenogenetically activated sea urchin eggs

Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of³H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the³H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the³H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of¹⁴C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction.     

Plant-microbe competition for soil amino acids in the alpine tundra: effects of freeze-thaw and dry-rewet events

Amino acids have been shown to be a potentially significant N source for the alpine sedge, Kobresia myosuroides. We hypothesised that freeze-thaw and dry-rewet events allow this plant species increased access to amino acids by disrupting microbial cells, which decreases the size of competing microbial populations, but increases soil amino acid concentrations. To test this hypothesis, we characterized freeze-thaw and dry-rewet events in the field and simulated them in laboratory experiments on plant-soil microcosms. In one experiment, ¹⁵N,¹³C-[2]-glycine was added to microcosms that had previously been subjected to a freeze-thaw or dry-rewet event, and isotopic concentrations in the plant and microbial fractions were compared to non-stressed controls. Microbial biomass and uptake of the labeled glycine were unaffected by the freezing and drying treatments, but microbial uptake of ¹⁵N was lower in the two warmer treatments (dry-rewet and summer control) then in the two colder treatments (freeze-thaw and fall control). Plant uptake of glycine-¹⁵N was decreased by climatic disturbance, and uptake in plants that had been frozen appeared to be dependent on the severity of the freeze. The fact that intact glycine was absorbed by the plants was confirmed by near equal enrichment of plant tissues in ¹³C and ¹⁵N. Plants under optimal conditions recovered 3.5% of the added ¹⁵N and microbes recovered 5.0%. The majority of the ¹³C and ¹⁵N label remained in a non-extractable fraction in the bulk soil. To better understand the isolated influences of environmental perturbations on soil amino acid pools and population sizes of amino-acid utilizing microbes, separate experiments were performed in which soils, alone, were subjected to drying and rewetting or freezing and thawing. Potential respiration of glycine and glutamate (substrate-induced respiration; SIR) by the soil microbial communities was unaffected by a single freeze-thaw event. Glycine SIR was decreased slightly (∼10%) by the most extreme drying treatment, but glutamate SIR was not significantly affected. Freezing lowered the concentration of water-extractable amino acids while drying increased their concentration. We interpret the surprising former result as either a decrease in proteolytic activity in frozen soils relative to amino acid uptake, or a stimulation in microbial uptake by physical nutrient release from the soil. We conclude that climatic disturbance does not provide opportunities for increased amino acid uptake by K. myosuroides, but that this plant competes well for amino acid N under non-stressed conditions, especially when soils are warm. We also note that this alpine tundra microbial community's high resistance to freeze-thaw and dry-rewet events is novel and contrasts with studies in other ecosystems. Received: 24 February 1997 / Accepted: 28 August 1997     

The transforming activity of sonicated Haemophilus influenzae DNA

Summary The inactivation of transforming Haemophilus influenzae DNA by sonication in aqueous solution was investigated. The molecular weight decrease of the molecules is the major factor in DNA inactivation. It impairs strongly the uptake of the DNA by the recipient bacteria, especially when the molecular weight is lower than 3x10⁶ daltons. The uptake of sonicated DNA by the bacterial cells seems not to be further reduced when molecules of about 0.5x10⁶ daltons are submitted to further depolymerisation. However the transforming activity of these molecules is still sensitive to further sonication. The transforming activity of the sonicated DNA is related in the last resort to the intact length of the DNA molecules, at the level of their single-strand structure, available for recombination. Rupture by ultrasound was found to be twice as efficient in reducing transforming activity as a nick induced by pancreatic DNAse.     

Sodium-dependent uptake of taurine in encapsulated Staphylococcus aureus strain M

A novel uptake system for the unusual sulfonated amino acid taurine was discovered in the prokaryote, encapsulated Staphylococcus aureus strain M. This strain has been shown previously to contain taurine in its capsular polysaccharide. Taurine uptake by whole cells incubated in buffer showed a saturable dependency upon Na⁺ and taurine uptake was itself a saturable process, stimulated by glucose, and markedly affected by temperature. No evidence was found for the inducibility of taurine uptake. In the presence of 10 mM NaCl Lineweaver-Burk plots revealed a K_m of 42 μM and V_max of 4.6 nmol/min per mg dry weight for taurine uptake at 37°C. Increasing concentrations of Na⁺ decreased the K_m of the system and appeared to increase the V_max. Of various other cations tested only Li⁺ supported marked taurine uptake. Excess unlabelled taurine did not cause efflux of radioactivity taken up. Taurine was taken up into cold trichloroacetic acid-soluble material and did not chromatograph as taurine, indicating rapid metabolism during or closely following uptake. Taurine uptake appeared to occur via a highly specific system because amino acids representing the major known groups of amino acid transport systems in S. aureus did not inhibit taurine uptake, and uptake was only slightly diminished by the structurally closely related compounds hypotaurine and 3-amino-1-propane sulfonic acid. Sulfhydryl group reagents, electron transport inhibitors, an uncoupler and inhibitors of Na⁺-linked transport processes inhibited taurine uptake. A variety of other metabolic inhibitors had little effect on taurine uptake.     

Auxin carriers in Cucurbita vesicles

Carrier-mediated uptake of indole-3-acetic acid (IAA) by microsomal vesicles from Cucurbita pepo L. hypocotyls was strongly inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D; i ₅₀= 0.3 M) but only weakly by 1-naphthylacetic acid (NAA). The fully ionised auxin indol-3-yl methanesulphonic acid also inhibited (i ₅₀=3 M). The same affinity ranking of these auxins for the uptake carrier, an electroimpelled auxin anion-H⁺ symport, is demonstrable in hypocotyl segments. The specificity of the auxin-anion eflux carrier was tested by the ability of different nonradioactive auxins to compete with [³H]IAA and reduce the stimulation of net radioactive uptake by N-1-naphthylphthalamic acid (NPA), a noncompetitive inhibitor of this carrier. By this criterion, NAA and IAA had comparable affinities, with 2,4-D interaction more weakly. Stimulation of [³H]IAA uptake by NAA, as a result of competition for the efflux carrier, could also be demonstrated when a suitable concentration of 2,4-D was used selectively to inhibit the uptake carrier. However, when [³H]NAA was used, no stimulation of its association with vesicles by NPA, 2,3,5-triiodobenzoic acid, or nonradioactive NAA was found. In hypocotyl segments, [³H]NAA net uptake was much less sensitive to NPA stimulation than was [¹⁴C]IAA uptake. The apparent contradictions concerning NAA could be explained by carrier-mediated auxin efflux making a smaller relative contribution to the overall transport of NAA than of IAA. The relationship between carrier specificity as manifested in vitro and the specificity of polar auxin transport is discussed.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - ION3 mixture of 4 M carbonylcyanide m-chlorophenylhydrazone, nigericin and valinomycin - IMS indol-3-yl methanesulphonic acid - NAA 1-naphthylacetic aci - NPA N-1-naphthylphthalamic acid     

Effects of chelating agents on the initial interaction of phytohemagglutinin with lymphocytes and the subsequent stimulation of amino acid uptake

The chelating agents, ethylene glycol bis-(β-aminoethyl ether)-N,N′-tetraacetic acid (EGTA) and EDTA, had no effect on the initial interaction of phytohemagglutinin with lymphocytes at concentrations which have been shown previously to inhibit the development of the phytohemagglutinin response completely. However, they had a marked inhibitory effect on uptake of the amino acid analog, α-aminoisobutyric acid in both unstimulated and phytohemagglutinin-stimulated cells. The inhibition of amino acid uptake by EGTA could be reversed by adding Ca²⁺ but not Mg²⁺. These results demonstrated that Ca²⁺ is not essential to the initial interaction of phytohemagglutinin with the cell, but does influence amino acid transport which may be a critical preparatory event for later increased protein synthesis.     

Conditions that affect binding of DNA by cultured plant cells and protoplasts: An autoradiographic analysis

Summary The binding of the¹⁴C-labelledSalmonella typhimurium DNA or³H-labelled soybean SB-1 DNA to cultured soybean cells (Glycine max L. Merr.) (SB-1) could be increased at least 100-fold by choosing the proper incubation conditions. The uptake of DNA by cells could completely be inhibited by the addition of an excess of unlabelled thymidine, indicating that the observed uptake of DNA by cells most probably is simply uptake of DNA degradation products. Autoradiograms, prepared from SB-1 protoplasts that were previously incubated with DNA, showed that the DNA was not associated with the protoplasts, but only with aggregates of cell wall material contaminating the protoplast preparation. When protoplasts and DNA were incubated in the presence of DEAE-dextran, the amount of DNAse resistant radioactivity increased 40 times. Again, the autoradiograms showed that most if not all DNAse-resistant material was associated with cell wall materials. Our observation that it is cell wall contaminants in protoplast preparations which account for most of the DNA binding demonstrates the need for caution in interpreting experiments on the binding and uptake of DNA by plant protoplasts.NRCC No. 16353.     

Transfection of Mycobacterium smegmatis SN2 with mycobacteriophage I3 DNA

Mycobacterium smegmatis SN2 does not exhibit natural competence for the uptake of phage I3 DNA. Competence can artificially be induced by treatment with glycine or CaCl₂, and the combination of both is even more effective. The efficiency of transfection can be improved by inclusion of protamine sulphate and heterologous RNA in the system. From ³²P DNA uptake studies the major barrier for the entry of DNA has been found to be the complex cell wall. The efficiency of transfection calculated on the basis of fraction of DNA which has entered the cell is comparable to that of other bacterial systems. The phage development takes a longer time (7 h for one cycle) after transfection, as compared to infection (4 h).     

L-alanine transport in isolated cells of interscapular brown adipose tissue in rat

The pattern of L-alanine uptake in isolated cells of interscapular brown adipose tissue has been determined. The uptake can be divided into the diffusion component (Kd=0.55 min^–1) and a saturable Na⁺-dependent transport (K _M =0.87 mM andV _max=155 nmol/min/10⁶ cells). The saturable component can be subdivided into MeAIB-sensitive (K _M =1.63 mM andV _max=162 nmol/min/10⁶ cells) and MeAIB-insensitive (K _M =3.2 mM andV _max=39.5 nmol/min/10⁶ cells). This kinetic pattern could indicate the presence of transport system (s) that resemble the commonly described transport systems for alanine uptake in several tissues.Abbreviations MeAIB Methyl-aminoisobutyric acid - AIB Aminoisobutyric acid     

Modeling of Cellular Arginine Uptake by More Than One Transporter

Determining the kinetic constants of arginine uptake by endothelial cells mediated by more than one transporter from linearization of data as Eadie-Hofstee plots or modeling which does not include the concentration of trace radiolabeled amino acid used to measure uptake may not be correct. The initial rate of uptake of trace [³H]l-arginine by HUVECs and ECV₃₀₄ cells in the presence of a range of unlabeled arginine and modifiers was used in nonlinear models to calculate the constants of arginine uptake using GraphPad Prism. Theoretical plots of uptake derived from constants determined from Eadie-Hofstee graphs overestimated uptake, whereas those from the nonlinear modeling approach agreed with experimental data. The contribution of uptake by individual transporters could be modeled and showed that leucine inhibited the individual transporters differently and not necessarily competitively. N-Ethylmaleimide inhibited only y⁺ transport, and BCH may be a selective inhibitor of y⁺L transport. The absence of sodium reduced arginine uptake by y⁺L transport and reduced the K _m′, whereas reducing sodium decreased arginine uptake by y⁺ transport without affecting the K _m′. The nonlinear modeling approach using raw data avoided the errors inherent in methods deriving constants from the linearization of the uptake processes following Michaelian kinetics. This study provides explanations for discrepancies in the literature and suggests that a nonlinear modeling approach better characterizes the kinetics of amino acid uptake into cells by more than one transporter.     

The effects of weak acids on potassium uptake by Escherichia coli K-12. Inhibition by low cytoplasmic pH

The activity of the Escherichia coli K⁺ transport system TrkA was measured as a function of the cytoplasmic pH of the cell. For this purpose, pH_in was decreased by the addition of the weak acids acetic acid, benzoic acid or salicylic acid to K⁺-depleted cells. Under these conditions, the initial rate of K⁺ uptake decreased strongly with pH_in, and was almost independent of the acid used. This inhibition was due to a strong decrease in the V_max for K⁺ uptake, which indicates that low cytoplasmic pH inactivates the TrkA K⁺ uptake system. The relevance of this inhibition for growth and metabolism at low pH_in is discussed.     

Auxin carriers in membranes of lupin hypocotyls

The pH-driven accumulation of [³H]indolyl-3-acetic acid (IAA) has been found to occur in membrane vesicles of lupin (Lupinus albus L.) hypocotyls. Most of this association of auxin with membranes is very sensitive to osmotic shock, high concentrations of permeable weak acids, incubation at 20° C for 20 min and to some ionophores. Long incubation times also depress the ability to accumulate radioactive IAA but this ability can be partially restored by a treatment that presumably reconstitutes the pH gradient across the membranes. Two specific inhibitors of auxin transport, N-1-naphtylphthalamic acid and 2,3,5-triiodobenzoic acid, stimulate net IAA uptake with an optimum at about 10^-6 M (pH 5.0). At least two auxin carriers appear to be present in the lupin membrane vesicles. An uptake carrier seems to be saturated at 10^-7 M IAA in the presence of N-1-naphtylphthalamic acid, but higher IAA concentrations are needed to saturate an efflux carrier. The uptake carrier also shows a high affinity for IAA and 2,4-dichlorophenoxyacetic acid and a low affinity for 1-naphthylacetic acid.Abbreviations CCCP carbonylcyanide m-chlorophenylhydrazone - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indolyl-3-acetic acid - NAA naphthalene-1-acetic acid - NIG nigeriein - NPA N-1-naphthylphthalamic acid - TIBA 2,3,5-triiodobenzoic acid - VAL valinomycin     

Inhibition of Synaptosomal Neurotransmitter Uptake by Hallucinogens

The effect of 13 hallucinogens on the uptake of serotonin and norepinephrine into hippocampal synaptosomes and of serotonin and dopamine into caudate synaptosomes was found to be inhibitory, except for lysergic acid diethylamide and 2-bromolysergic acid diethylamide, which were inactive. The indoleal-kylamines were generally more potent than the phenylethylamines. The reported inhibition of uptake of serotonin by 5-methoxy-N,N-dimethyltryptamine and lysergic acid diethylamide into whole brain synaptosomes was not reproducible at concentrations 10² to 10⁴ times higher than those stated in the literature.