Enhancement of ouabain and calcium ionophore A23187 of outward transport of polyamines from lymphocytes

Micellar electrokinetic chromatography of polyamines and monoacetylpolyamines

A selective procedure for qualitative and quantitative analysis of ten polyamines by micellar electrokinetic chromatography (MEKC) was developed. Benzoylated polyamines and acetylpolyamines in micellar phase of SDS (10 mM) were separated at 25 degrees C by 20 mM borate buffer pH 8.5, containing 8% ethanol, with an applied voltage of 25 kV (5 microA) and then detected at 198 nm. The experimental factors and operational parameters were optimized by performing analysis at different surfactant concentrations, pH, voltage and temperature with and without ethanol. The repeatibility of migration times and peak heights is a peculiarity of the method here described.

Rapid and simultaneous high-performance liquid chromatography assay of polyamines and monoacetylpolyamines in biological specimens

A rapid, resolutive and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for polyamines and acetylpolyamines by adopting pre-column derivatization with benzoyl chloride. In a single run lasting less than 15 min ten polyamines were separated as well as traces of benzoic acid, methylbenzoate and benzoic anhydride. These contaminants, produced during the derivatization reaction, were almost all eliminated by washing steps envisaged in the same procedure. This simple and sensitive method can be applied to routine determination of polyamines in biological samples. A fine application of this procedure to the determination of endogenous content of polyamines in chick embryo retina was reported.

Characterization of a diamine exporter in Chinese hamster ovary cells and identification of specific polyamine substrates

Export of the diamine putrescine was studied using inside-out plasma membrane vesicles prepared from Chinese hamster cells. Putrescine uptake into vesicles was a saturable and an ATP- and antizyme-independent process. Excess amounts of a series of diamines or monoacetyl spermidine, but not monoacetyl putrescine, spermidine, or spermine, inhibited putrescine transport. Putrescine uptake into vesicles prepared at pH 7.4 was suppressed at pH 5, compared with pH 7.4; was stimulated approximately 2.5-fold at pH 7.4 in vesicles prepared at pH 6.25, compared with vesicles prepared at pH 7.4; and was not inhibited by valinomycin in the presence of potassium ions. Reserpine and verapamil blocked [3H]putrescine uptake into inverted vesicles. Verapamil treatment caused an increase in intracellular contents of putrescine, cadaverine, and N8-acetylspermidine, in unstressed proliferating cells, or of N1-acetylspermidine, in cells subjected to heat shock to induce acetylation of spermidine at N1. These data indicate that putrescine export in Chinese hamster cells is mediated by a non-electrogenic antiporter capable of using protons as the counter ion. Physiological substrates for this exporter include putrescine, cadaverine, and monoacetyl spermidine and have the general structure NH3+-(CH2)n-NH2 + R at acidic or neutral pH.

JAR human placental choriocarcinoma cells actively synthesize, take up and release polyamines

Uptake of polyamines has been investigated extensively in many cells, but not in placenta, where the polyamine-polyamine oxidase system is supposed to have an immunoregulatory function in pregnancy. Due to the importance of the transfer in this tissue, we have started this study. JAR human placental choriocarcinoma cells in monolayer at confluency were used as a model for measuring the key enzymes of polyamine synthesis and interconversion, rate of uptake and efflux, and the polyamine content. Polyamines were taken up by JAR cells and released by an independent mechanism. Ornithine decarboxylase and spermidine acetyltransferase activities and the rate of transport in and out of the cell were much higher than in other cells, such as L1210 cells. However the systems used for uptake and release appear in many respects to be similar to those observed in L1210 cells, but different from others. The uptake appears to be regulated by an inhibitory protein. Moreover, protein kinase C appears to be involved in the process. The efflux also is regulated as in L1210 cells, through control of H+ and Ca2+ concentration. In conclusion, this study shows that, in JAR cells, ornithine decarboxylase and spermidine acetyltransferase activities were much higher than in other cells, and so was the rate of transport in and out of the cells. As a result, a much higher polyamine content was observed.

Polyamine transport in mammalian cells. An update

The uptake and release of the natural polyamines putrescine, spermidine and spermine by mammalian cells are integral parts of the systems that regulate the intracellular concentrations of these biogenic amines according to needs. Although a general feature of all tissues, polyamine uptake into intestinal mucosa cells is perhaps the most obvious polyamine transport pathway of physiological and pathophysiological importance. Mutant cell lines lacking the ability to take up polyamines from the environment are capable of releasing polyamines. This indicates that uptake and release are functions of two different transport systems. The isolation of a transporter gene from a mammalian cell line is still lacking. Overaccumulation of polyamines is controlled by release and by a feedback regulation system that involves de novo synthesis of antizyme, a well known protein that also regulates the activity of ornithine decarboxylase. Recent work has demonstrated that Ca(2+)-signalling pathways are also involved. Although there is consensus about the importance of polyamine uptake inhibitors in the treatment of neoplastic disorders, a practically useful uptake inhibitor is still missing. However, the attempts to target tumours, and to increase the selectivity of cytotoxic agents by combining them with the polyamine structure, are promising. New, less toxic and more selective anticancer drugs can be expected from this approach.

Characterization of putrescine and cadaverine export in mammalian cells. A pharmacological approach

We characterized the mechanism(s) involved in the efflux of putrescine/cadaverine from cultured mammalian cells using various pharmacological agents. Verapamil and quinine inhibited putrescine and cadaverine export in monocytic-leukemic RAW 264 and H35 hepatoma cells in a concentration-dependent manner with an IC50 in the micromolar range. Verapamil, which inhibits L-type calcium channels, inhibited putrescine export, regardless of whether calcium was present in the extracellular medium or not. Furthermore, the export of putrescine in the absence of verapamil did not appear to depend upon extracellular calcium. Neither intracellular calcium, external sodium, changes in intracellular pH nor phosphorylation affected the levels of putrescine export independently from changes in intracellular putrescine levels. The data suggest that verapamil and quinine inhibit putrescine/cadaverine efflux from the cell by binding directly to an integral membrane protein.

Ornithine decarboxylase activity and polyamine concentrations in fetal rat brain: response to chronic hypoxic-hypoxia and/or carbon monoxide-hypoxia

Ornithine decarboxylase activity (ODC; E.C. 4.1.1.17), is significantly elevated in fetal and newborn rat brain in response to acute hypoxia. Because relatively little is known about ODC activities and polyamine metabolism in hypoxia and also because ODC and the polyamines are essential for normal growth and development, we examined the effect of chronic maternal hypoxic-hypoxia (16-10.5% O2), carbon monoxide-hypoxia (100-200 ppm CO) and their combination, on fetal weight, fetal brain ODC activity and polyamine concentrations. Time-dated pregnant Sprague-Dawley rats were chronically exposed to hypoxia from gestational day (E-15), to gestational day 21 (E-21), in individual chambers. Pair-fed controls were given an amount equivalent to that eaten by a hypoxic dam over the previous 24 h. We measured fetal weight, as well as brain ODC activity and polyamine concentrations on both E-19 and E-21. Pair-feeding had no effect on fetal weight, ODC activity or polyamine concentrations. On both E-19 and E-21, however, fetal weights were significantly reduced with higher levels of hypoxic-hypoxia (e.g., 10.5% O2). At 100 or 200 ppm, carbon monoxide alone appeared not to affect fetal weight; however, combined with even mild hypoxia (16% O2), fetal weights were reduced almost 20%, suggesting that together, CO- and hypoxic-hypoxia exert a synergistic effect of fetal weight decrements. (1) There was no consistent pattern of ODC activity changes which correlated to the fetal weight losses or levels of hypoxia. These results suggest that ODC activity may not be a good marker for chronic, as opposed to acute hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Ornithine decarboxylase activity in fetal and newborn rat brain: responses to hypoxic and carbon monoxide hypoxia

In response to acute maternal hypoxia, ornithine decarboxylase (ODC) activity increased significantly in fetal rat brain, peaking at 4 h. This was associated with increased ODC mRNA and elevated polyamine concentrations. To correlate this response with development, we measured ODC activity in the rat from gestational day E 17 to postnatal day P 10. We also examined to what extent hypoxia induces increased ODC activity in adult rat brains and whether the response to chronic hypoxia differed from that to acute hypoxia. To test the hypothesis that this increased activity is due to hypoxic hypoxia per se, we subjected pregnant dams to inspired carbon monoxide concentrations ranging from 150 to 1000 ppm and assayed ODC activity in the fetal brain 4 h later. In the fetus, ODC activity was elevated on E 17 in the cerebrum and cerebellum. It declined gradually to about one-tenth E 17 levels by E 21 and remained low thereafter except for a postnatal elevation in the cerebellum on P 3. In response to 10.5% O2, in the 3-day-old rat, ODC activity peaked between 2 and 3 h of hypoxia, increasing 3-fold in the hippocampus and 2-fold in cerebellum. Similar increases were seen in the hypoxic adult rat brain. In inspired oxygen dose-response studies, exposure of P 3 rat pups to 13.25% O2 for 2.5 h produced a 1.5-fold increase in ODC activity; 10.5% O2 produced a 2-3-fold increase while in response to 9% O2, ODC activity remained at baseline levels. With maternal CO-hypoxia, ODC activity increased in the fetal brain at 4 h, as seen with hypoxic-hypoxia. For example, in hippocampus, ODC activity doubled at 500 ppm and tripled at 600 ppm. We conclude: (1) apparently, the ability to respond thus is not lost as the animal ages and may represent an important cellular response to acute hypoxia; (2) the increase in hypoxic-induced ODC activity is relative to the already elevated activity seen from E 17 to E 20; a vast reserve for the induction of fetal ODC activity probably exists and may indicate the importance of this enzyme during this time frame for differentiation and growth promotion; and (3) the CO-hypoxia studies suggest that some aspects of the cellular responses to CO- and hypoxic-hypoxia are similar.

A free-radical hypothesis for the instability and evolution of genotype and phenotype in vitro

It has been known for several decades that cultured murine cells undergo a defined series of changes, i.e., an in vitro evolution, which includes crisis, spontaneous transformation ('immortalization'), aneuploidy, and spontaneous neoplastic transformation. These changes have been shown to be caused by the in vitro environment rather than an inherent instability of the murine phenotype or genotype. Serum amine oxidases were recently identified as a predominant cause of crisis. These enzymes generate hydrogen peroxide from polyamine substrates that enter the extracellular milieu. This finding implicates free-radical toxicity as the underlying cause of in vitro evolution. We propose an oxyradical hypothesis to explain each of the stages of in vitro evolution and discuss its significance for cytotechnology and long-term cultivation of mammalian cell types.

Efflux of polyamines from human lymphocytes and from L 1210 cells

1. In human lymphocytes alkalinization of the cytoplasm with monensin or NH4Cl promotes release of polyamines. The effect of NH4Cl is abolished by EGTA and diltiazem. 2. Concanavalin A also promotes an increase of the efflux, counteracted again by EGTA and diltiazem. 3. By effect of TPA, polyamine efflux is decreased in the first 90 min, and later increased. The activation is partially prevented by H7 and by sphingosine. 4. In contrast with human lymphocytes, L 1210 cells release actively endogenous polyamines, but slowly radioactive polyamines. 5. Concanavalin A does not activate the latter process; A 23187 and NH4Cl on the contrary promote a much higher increase in the efflux rate than in normal lymphocytes. EGTA and diltiazem partially counteract the effect of NH4Cl on the release of radioactivity.

Transport of putrescine in the isolated rabbit intestine

The transepithelial fluxes of putrescine were studied in sections of the three segments of rabbit intestine mounted in an Ussing chamber. The ileum exhibited the highest mucosal-to-serosal (Jms) and serosal-to-mucosal (Jsm) unidirectional fluxes of 1 mumol/l [3H]putrescine. Putrescine net flux (Jnet = Jms - Jsm) was deduced to be positive through the duodenum (Jnet = 53.40 +/- 14.30 pmol h-1 cm-2), not significantly different from zero through the jejunum (Jnet = 8.90 +/- 19.20 pmol h-1 cm-2) and negative through the ileum (Jnet = -34.30 +/- 13.80 pmol h-1 cm-2). Increasing putrescine concentration up to 10 mmol/l led to an increase in Jms, Jsm and Jnet without affecting the transport polarity in the ileum. The tissue retention of putrescine after 100 min was higher by the serosal side than by the mucosal side of the ileum. In parallel experiments, isolated pieces of ileum accumulated putrescine to a five- to sixfold concentration gradient by a ouabain-inhibitable mechanism. In contrast with arginine and in order of decreasing potency, putrescine, cystamine (a transglutaminase inhibitor), spermidine and spermine (1 mmol/l) reduced both unidirectional fluxes of putrescine across the ileum in the Ussing chamber. The latter effectors, except spermine, and N,N-dimethylcasein (1 mg/ml) led to an important, if not complete, suppression of putrescine secretion by the ileum, while the calmodulin antagonist melittin (0.3 micrograms/ml) reversed the polarity of polyamine transport, suggesting the involvement of transglutaminase in putrescine transport. We conclude that the heterogeneous pattern of putrescine transport along the small-intestinal epithelium constitutes an important feature of the regulation of polyamine concentrations in this tissue.