Oxidative reactivity of the tryptophan metabolites 3-hydroxyanthranilate, cinnabarinate, quinolinate and picolinate

The oxidative reactivities of four tryptophan metabolites in the kynurenine pathway were examined as a potential mechanism for their reported neurotoxicities and carcinogenicities. Neither quinolinic acid, a neurotoxin, nor its monocarboxylic analogue, picolinic acid, auto-oxidized over a wide pH range. However, 3-hydroxyanthranilic acid (3-HAT), a carcinogen, readily auto-oxidized and the reaction rate increased exponentially with increasing pH. 3-HAT auto-oxidation likely involves two steps: auto-oxidation of 3-HAT to the semiquinoneimine (anthranilyl radical) which oxidizes to the quinoneimine, followed by condensation and oxidation reactions to yield a second carcinogen, cinnabarinic acid. 3-HAT auto-oxidation to cinnabarinate required molecular oxygen and generated superoxide radicals and H2O2. Superoxide dismutase (SOD) accelerated 3-HAT auto-oxidation 4-fold, probably by preventing back reactions between superoxide and either the anthranilyl radical or the quinoneimine formed during the initial step of auto-oxidation. Catalase did not accelerate 3-HAT auto-oxidation, but it did prevent destruction of cinnabarinate by H2O2. Interconversion between oxyhemoglobin and methemoglobin occurred during 3-HAT auto-oxidation, although neither form of hemoglobin altered rates of 3-HAT auto-oxidation. Mn2+, Mn3+ and Fe3+-EDTA did not directly catalyze cinnabarinate formation in the absence of O2, but they did accelerate cinnabarinate formation under aerobic conditions.     

Interdependence of hemoglobin, catalase and the hexose monophosphate shunt in red blood cells exposed to oxidative agents

Hydrogen peroxide, 1, 4-naphthoquinone-2-sulfonic acid and 6-hydroxydopamine were used as biochemical probes to study the interdependence of hemoglobin, catalase and the hexose monophosphate shunt in protection of red blood cell (red cell) function against Superoxide, hydrogen peroxide and organic free radicals. It was shown that catalase may remove hydrogen peroxide both catalatically and peroxidatically in the red cell and that glucose metabolism supplies electron donors for the peroxidatic function of catalase. The hexose monophosphate shunt is known to participate in removal of hydrogen peroxide by supplying electrons for the action of glutathione reductase and glutathione peroxidase. Experiments in which red cell catalase was irreversibly inhibited by interaction with hydrogen peroxide and 3-amino-1, 2, 4-triazole showed that both catalase and the hexose monophosphate shunt share in the removal of hydrogen peroxide from red cells. The effect of the hemoglobin oxidation state on the interaction of red cells and oxidative agents was studied using red cell preparations containing hemoglobin, carbonmonoxyhemoglobin or methemoglobin. Oxyhemoglobin was able to accelerate the production of Superoxide and hydrogen peroxide with agents like 1, 4-naphthoquinone-2-sulfonic acid, whereas oxyhemoglobin had little effect with 6-hydroxydopamine. In experiments with red cells containing oxyhemoglobin, the accumulation of catalase in the form of Compound II, with resulting loss of available catalatic activity, was directly proportional to formation of methemoglobin. The close relationship between loss of catalatic activity and formation of methemoglobin may indicate that catalase has a protective effect on hemoglobin. Experiments with red cells containing methemoglobin indicated that once methemoglobin is formed it protects the red cell from further loss of the catalatic activity of catalase. In some circumstances oxyhemoglobin was formed from methemoglobin as a by-product of the protective effect of methemoglobin on red cell function. Formation of oxyhemoglobin by this mechanism was many times faster than oxyhemoglobin formation by the methemoglobin reductase system.     

Styrene oxide in blood, hemoglobin adducts, and urinary metabolites in human volunteers exposed to (13)C(8)-styrene vapors

Styrene is used in the manufacture of plastics and polymers and in the boat-building industry. The major metabolic route for styrene in rats, mice, and humans involves conversion to styrene-7,8-oxide (SO). The purpose of this study was to evaluate blood SO, SO-hemoglobin (SO-Hb) adducts, and urinary metabolites in styrene-exposed human volunteers and to compare these results with data previously obtained for rodents. Four healthy male volunteers were exposed for 2 h during light physical exercise to 50 ppm (13)C(8)-styrene vapor via a face mask. Levels and time profiles of styrene in exhaled air, blood, and urine (analyzed by GC) and urinary excretion patterns of mandelic acid and phenylglyoxylic acid in urine (analyzed by HPLC) were comparable to previously published volunteer studies. Maximum levels of SO in blood (measured by GC-MS) of 2.5-12.2 (average 6.7) nM were seen after 2 h, i.e., in the first sample collected after exposure had ended. The styrene blood level in humans was about 1.5 to 2 times higher than in rats and 4 times higher than in mice for equivalent styrene exposures. In contrast the SO levels in human blood was approximately fourfold lower than in mice. The level of hydroxyphenethylvaline (determined by GC-MS-MS) in pooled blood collected after exposure was estimated as 0.3 pmol/g globin corresponding to a SO-Hb adduct increment of about 0.003 pmol/g and ppmh. NMR analyses of urine showed that a major portion (> 95%) of the excreted (13)C-derived metabolites was derived from hydrolysis of SO, while only a small percentage of the excreted metabolites (< 5%) was derived from metabolism via phenylacetaldehyde. Signals consistent with metabolites derived from other pathways of styrene metabolism in rodents (such as glutathione conjugation with SO or ring epoxidation) were not detected.     

Glucose metabolism of oxidatively stressed human red blood cells incubated in plasma or medium containing physiologic concentrations of lactate,pyruvate and ascorbate

Red cells suspended in either defined medium or buffered plasma were oxidatively stressed by incubation in the presence of 1, 4-naphthoquinone-2-sulfonate at concentrations which caused less than 50% methemoglobin accumulation, stimulation of the hexose monophosphate shunt to less than 15% of capacity, and about a 30% increase in flux through glycolysis. Normal plasma concentrations of lactate and pyruvate in either defined medium or buffered plasma allowed increased contribution of reducing equivalents from glycolysis in response to oxidative stress. Increased utilization of reducing equivalents by the red cell was observed as increased accumulation of pyruvate, whereas accumulation of lactate represented storage of reducing equivalents. Exogenous lactate or pyruvate did not serve as a net electron source or sink since the total content in red cell suspensions of both lactate and pyruvate was increased during exposure to oxidative stress. If exogenous lactate had been used as a net source of reducing equivalents, the lactate concentration would have decreased during incubation of red cell suspensions. Plasma ascorbate or other constituents did not alter the qualitative response of glycolysis to oxidative stress (decreased lactate accumulation, increased pyruvate accumulation, and increased total flux through glycolysis), but plasma constituents did raise significantly the dose of oxidant agent required to elicit a given quantitative response. At levels of oxidative stress likely to be encountered in vivo, glycolysis and the hexose monophosphate shunt may be equal in importance as aerobic/antioxidant pathways.     

Pyruvate kinase is protected by glutathione-dependent redox balance in human red blood cells exposed to reactive oxygen species

To determine the antioxidant role of glutathione (GSH) in human red blood cells (RBCs), we investigated the effect of disrupting GSH homeostasis on the oxidative modification of thiol-dependent enzymes by exposure to tert-butyl hydroperoxide (BHP). When hemolysate was incubated with BHP, significant decreases in enzyme activity were observed. However, the inactivation did not occur in intact RBC suspensions that were exposed to BHP. In this study, we used two independent treatments aimed at decreasing the level of reduced form of GSH, pre-incubation with a glutathione reductase inhibitor or glucose-free medium to examine the influences of preventing GSH-dependent antioxidant and reactivation activity on thiol-dependent enzyme. Pyruvate kinase (PK) activity clearly decreased along with depletion of GSH compared to other glycolytic enzyme activities by BHP exposure in RBCs. The addition of GSH, but not glucose, before BHP exposure completely prevented the inactivation of PK in hemolysate; however, partial reactivation of inactivated PK was observed by post-addition of both GSH and glutaredoxin at an early stage during BHP exposure. Moreover, hydroxyl radicals but not hydrogen peroxide inactivated PK. These results suggest that PK is highly susceptible to radicals and that GSH is essential to protect PK activity by not only directly scavenging radicals but also by systematically reactivating oxidized enzyme in human RBCs.     

RP-HPLC法测定全血、血浆和红细胞中氯氮平及2种主要代谢物

目的建立一种测定全血、血浆和红细胞中氯氮平(CZP)、N-去甲基氯氮平(N-CZP)和氯氮平N-氧化物(CZP-NO)浓度的RP-HPLC法.方法标本用乙酸乙酯提取后再经0.1mol·L-1盐酸反提取,以利培酮为内标,流动相为甲醇-乙腈-水(16.0∶36.5∶47.5),色谱柱为Inertsil-ODS-3柱,柱温为40℃,检测波长为254nm,流速为0.9mL*min-1.结果全血、血浆和红细胞中CZP和N-CZP的最低检测浓度均为7μg*L-1;血浆中CZP-NO的最低检测浓度为13μg*L-1,全血和红细胞中为14μg*L-1.全血、血浆和红细胞中CZP和N-CZP的绝对回收率均为85%～95%,血浆中CZP-NO的绝对回收率>82%,全血和红细胞中CZP-NO的绝对回收率约为70%.日内和日间RSD均小于7%.结论本法操作简便,灵敏度高,重复性好,适合于临床检测.     

Activation of alveolar macrophages and peripheral red blood cells in rats exposed to fibers/particles

The cytotoxic and oxidative responses of crocidolite and chrysotile asbestos fibers and ultrafine titanium dioxide (UF–TiO₂) particles were measured in alveolar macrophages (AM) and peripheral red blood cells (RBC) of rat after 30 days with a single intratracheal exposure (5 mg). The following responses were observed one month after fiber/particle instillation: (1) AM population increased; (2) lactate dehydrogenase and acid phosphatase activities in cell free lung lavage fluid increased; (3) substances that react with hydrogen peroxide or thiobarbituric acid were elevated in both AM and peripheral RBC; (4) glutathione peroxidase, glutathione reductase, and catalase were altered in both AM and peripheral RBC; (5) glutathione and ascorbic acid decreased in both AM and peripheral RBC. A significant difference from negative controls was noted in all responses of the two fiber-exposed groups, and in most responses of the UF–TiO₂-exposed group. The level of responses to the three test substances suggested a decreasing order of toxicity, with crocidolite>chrysotile>UF–TiO₂.     

肾移植后环孢素A血药浓度与红细胞及血红蛋白的相关性分析

目的 探讨肾移植受者术后ＣｓＡ血药浓度与ＢＲＣ数及ＨＧＣ含量的相关性。方法 应用ＦＰＩＡ法测定４０例肾移植受者术后ＣｓＡ血药浓度,分析术后不同时间ＲＢＣ数及ＨＧＢ含量对ＣｓＡ血药浓度的影响。结果 在术后早期ＣｓＡ用量基本不变的情况下,ＣｓＡ血药浓度与ＲＢＣ数及ＨＧＢ含量有显著正相关。结论 术后早期ＲＢＣ和ＨＧＢ可能是影响ＣｓＡ血药浓度的因素之一。     

2,5-Hexanedione modifies skeletal proteins of the red blood cells and increases the binding of hemoglobin to the membrane

The effects of 2,5-hexanedione (2,5 HD) on skeletal proteins of red blood cells (RBCs) were investigated both in vitro (human RBCs) and in vivo in male Sprague-Dawley rats which had been treated with the drug for several days. We found that 2,5 HD induced the following major changes in the electrophoretic pattern of the skeletal proteins: (i) the appearance of high-molecular weight bands, (ii) a dose-dependent decrease in spectrin Bands 1 and 2, and (iii) a dose-dependent increase in the amount of hemoglobin (Hb) associated with the membrane. Membranoskeletons, prepared from resealed ghosts which had been previously treated with 2,5 HD, were able to bind an increased amount of Hb from untreated RBCs, thus suggesting a drug-induced modification of the membrane. Extraction of spectrin and actin from ghosts did not remove the membrane-bound Hb and, furthermore, Hb bound to 2,5 HD-treated membranes mainly bearing Band 3 and free of peripheral proteins. These data suggested a 2,5 HD-induced modification of an intrinsic membrane protein, probably Band 3. This hypothesis was consistent with the observation that 2,5 HD also induced a modification of Band 3 aminogroups, as evidenced by a dose-dependent decrease in the binding of eosin probes. Furthermore, RBCs treated in vitro with 2,5 HD bound an increased amount of autologous immunoglobulins (IgG). As reported by Kay and Low et al. the binding of autologous IgG is a phenomenon associated with the aging process of RBCs and may involve a modification of Band 3. Our data show that RBCs treated with 2,5 HD acquired various characteristics of senescent cells such as spectrin cross-linking, Hb-membrane binding and increased IgG binding, and suggest that 2,5 HD treatment might affect RBC survival.     

Effects of physiologic concentrations of lactate, pyruvate and ascorbate on glucose metabolism in unstressed and oxidatively stressed human red blood cells

Glucose metabolism was studied in human red blood cells incubated in the presence of physiologic concentrations of ascorbate (0.1 mM) and/or lactate (2 mM) plus pyruvate (0.1 mM). The total flux through glycolysis, as measured by 14C-labeling of glycolytic intermediates, was increased about 15% by ascorbate, 30% by lactate plus pyruvate, and 40% by ascorbate plus lactate plus pyruvate. We found, however, that physiologic concentrations of ascorbate and/or lactate plus pyruvate had no effect on flux of glucose or recycling of pentoses through the hexose monophosphate shunt. Increased formation of lactate accounted for most of the observed increase in glycolysis with little change in pyruvate formation, indicating that the increased flux of reducing equivalents from glucose was stored as lactate rather than being consumed by red cell metabolism. In all experiments, there was a net increase with time in the absolute amount of both lactate and pyruvate in red cell suspensions, indicating that lactate or pyruvate present at zero time did not function as a stoichiometric source or sink for reducing equivalents. There was little effect on steady-state levels of ATP or 2,3-diphosphoglycerate. Equilibration of ascorbate between red cells and the medium was complete before the addition of 14C-labeled glucose to the medium. Glucose metabolism prevented net oxidation of ascorbate in the incubation medium. Physiologic concentrations of ascorbate, lactate and pyruvate appear to increase flux through glycolysis by increasing the turnover of ATP and/or 2,3-diphosphoglycerate. Red cells were exposed to mild oxidative stress by incubation with 0.27 mM 6-hydroxydopamine, 0.27 mM 6-aminodopamine, 0.13 mM 1,4-naphthoquinone-2-sulfonic acid or 0.27 mM phenylhydrazine. The metabolic response to oxidative stress was determined by measuring the formation of methemoglobin, pyruvate, lactate and CO2 in the presence and absence of physiologic concentrations of lactate, pyruvate and ascorbate. Lactate, pyruvate and ascorbate had no effect on the net methemoglobin accumulation but rather on the distribution of the metabolic sources of reducing equivalents and on the flux of reducing equivalents to oxygen. Physiologic lactate and pyruvate allowed increased flow of reducing equivalents from glycolysis to methemoglobin and ultimately oxygen without the necessity of increased flux through glycolysis. This was accomplished by a decrease in the ratio of newly formed lactate to newly formed pyruvate with no increase in total lactate plus pyruvate.(ABSTRACT TRUNCATED AT 400 WORDS)     

HPLC法测定人红细胞中的S-腺苷同型半胱氨酸和S-腺苷甲硫氨酸

目的建立HPLC法测定人红细胞中S-腺苷同型半胱氨酸(SAH)和S-腺苷甲硫氨酸(SAM)浓度的方法。方法人红细胞经同体积醋酸盐缓冲液稀释后,经10%高氯酸蛋白沉淀后直接进样。采用Athena C18 WP柱(150 mm×4.6 mm,3μm),柱温35℃,流动相为含5 mmol·L-1庚烷磺酸钠的50 mmol·L-1 Na H2PO4缓冲液(pH 4.0)-甲醇(80:20,v/v),流速:1.0 m L·min-1,检测波长254 nm。采用外标法定量。结果SAH和SAM分别在0.025~10 mg·L-1和0.05~20 mg·L-1内线性关系良好,SAH和SAM的日内、日间RSD均<12%,加样回收率在95.5%~106.3%,样品提取后在24 h内稳定性良好。结论该法快速、简便、准确,适用于SAH和SAM的体内分析检测。     

Halothane inhibits hyperpolarization and potassium channels in human red blood cells

The effect of halothane on the Ca2+-sensitive K+ channel in human erythrocytes has been investigated. The red cells were suspended in buffer-free salt solutions containing Ca2+ or 45Ca2+. The protonophore CCCP was added to bring about a rapid equilibration of protons across the plasma membrane. After addition of the divalent cation ionophore A23187, the cells took up Ca2+ and this caused the K+ channels to open. When the medium contained 1 mM K+, the addition of A23187 induced a transient hyperpolarization of the cells, as monitored by measurement of the pH of the medium. The cellular pH, being buffered by haemoglobin, was virtually constant. Halothane reversibly inhibited hyperpolarization and limited the release of cellular K+ in a dose-dependent way, but did not inhibit the Ca2+-transporting properties of A23187. No stimulatory effects of halothane were observed even at low halothane concentrations. In conclusion, halothane reversibly inhibits the Ca2+-sensitive K+ channel in human erythrocytes with an ED50 of about 0.5 mM.     

Inhibition of the Cl-/NaCO3- anion exchanger by xipamide in human red blood cells

The mechanism of action of classical loop diuretics of the 2- or 3-amino-5-sulfamoylbenzoic acid and (aryloxy)acetic acid families involves competition with chloride for a common site on the (Na+, K+, 2Cl-) co-transport system. However this is not the mechanism of action of some high-ceiling diuretics like muzolimine, MK 473, xipamide, indapamide and clopamide, which are not carboxylic acids. We evaluated three of these latter diuretics (xipamide, muzolimine and clopamide) for their inhibitory effects on five ion transport systems in human red blood cells: (i) Cl(-)-dependent (Na+, K+) co-transport, (ii) (NaCO3-/Cl-) anion exchanger, (iii) (Cl-, K+) co-transport, (iv) Na+, K+ pump and (v) Na+: Li+ counter-transport; and on one ion channel the Ca2+-dependent, K+ channel. All erythrocyte transport pathways were resistant to the three diuretics studied (IC50 of 10(-3) M or higher) with one remarkable exception, the (NaCO3-/Cl-) anion exchanger. This transport system was inhibited by xipamide (IC50 of 2.5 +/- 0.4 X 10(-5) M, mean +/- S.D. of five experiments) and less potently by muzolimine (IC50 of 1.1 +/- 0.3 X 10(-4) M, mean +/- S.D. of three experiments). Clopamide only inhibited the anion exchanger at high concentrations (IC50 of about 10(-3) M). Xipamide, the most potent diuretic in this test, was at least one order of magnitude more active than furosemide, ethacrynic acid, hydrochlorothiazide and amiloride. Inhibition of the anion carrier could be involved in the diuretic action (inhibition of CO2-stimulated NaCl absorption in the TAL) and/or in the antihypertensive action (inhibition of net NaCO3- influx and secondarily of Ca2+ influx through Na+: Ca2+ exchange in vascular smooth muscle cells of xipamide).     

Mannan decelerates the clearance of human red blood cells in SCID mouse

Mannans and its related compounds decelerated human (Hu) red blood cell (RBC)-clearance in severe combined immunodeficiency (SCID) mice by inhibiting erythro-phagocytosis of macrophages. Chimeric SCID mice for Hu-RBC which are generated by repeated transfusions with mature Hu-RBCs are described recently as a model for Plasmodium falciparum infection, though the Hu-RBC clearance in the mice at present is very rapid and the parasitemia in the mice is only erratic. Here, we aimed to study the method to decelerate Hu-RBC clearance in SCID mice, to establish a suitable mouse model for malaria parasites. Yeast and Candida mannans as well as lactoferrin, a glycoprotein containing both oligomannoside- and N-acetyllactosamine-type glycans, decelerated Hu-RBC clearance, but instead other saccharides such as carboxymethyl chitin, N-acetylglucosamine, and d-glucose did not. Yeast mannan and lactoferrin interfered significantly with in vitro Hu-RBC-phagocytosis which was also inhibited by mannopentaose and mannotoriose. d-mannose exhibited a moderate inhibitory activity. N-acetyl-d-glucosamine, however, showed only a slight inhibitory activity, but d-glucose had no inhibitory activity on Hu-RBC phagocytosis. These results may postulate that Hu-RBC clearance in SCID mouse might be mediated by receptor–ligand binding by a macrophage lectin like receptor with mannose specificity.     

Effects of nine synthetic putative metabolites of primaquine on activity of the hexose monophosphate shunt in intact human red blood cells in vitro

Suspensions of washed human red blood cells were treated with nine synthetic putative metabolic derivatives of primaquine (PQ'), and their individual effects on activity of the hexose monophosphate shunt (HMS) were quantitated by radiometric analysis of 14CO2 from [14C] glucose. The most potent HMS stimulant was 5-hydroxy-6-methoxy-8-aminoquinoline (5H6MQ), which caused 10-fold elevation of HMS activity at an estimated concentration of 0.004 mM. Ten millimolar primaquine (PQ) was required to achieve the same effect. Thus, 5H6MQ was approximately 2500-fold more reactive with the HMS than PQ. Other analogs achieved less than 0.4- to 154-fold increases in HMS reactivity. Patterns of effects on HMS activity indicated that 5-hydroxylation and/or N-dealkylation of PQ strongly enhanced HMS reactivity. In contrast, none of the putative metabolites of PQ activated the proteolytic system known to degrade oxidized protein in red cells, indicating that stimulation of the HMS by the PQ analogs was not related to an injurious oxidative stress. Red cells pretreated with 1.0 mM N-ethylmaleimide (NEM) or with 1.0% (w/v) sodium nitrite to cause glutathione sulfhydryl blockage and conversion of red cell hemoglobin to methemoglobin (metHb), respectively, also showed elevation of HMS activity when exposed to 5H6MQ. These observations suggested that 5H6MQ-induced elevation of HMS activity was at least partially independent of glutathione redox reactions, hydrogen peroxide accumulation and reaction with oxyhemoglobin. The relevance of these observations to proposed mechanisms of hemolytic toxicity of PQ is discussed.     

Absence of adverse effect on thyroid function and red blood cells in a population of workers exposed to cobalt compounds

Context

Hypothyroidism has been observed in the fifties and sixties as an undesirable side-effect of cobalt therapy used for its erythropoietic properties in the treatment of anemia.

Objective

This study aims at evaluating the possible impact of both cumulative (long-term) and recent occupational exposure to cobalt on thyroid function and red blood cells.

Methods and setting

A cross-sectional survey was conducted from February 2008 to August 2009 in a population of 249 male workers from a cobalt production department in the North of Belgium. The possible effect of cobalt exposure on thyroid and red blood cells was investigated through multiple regression analyses.

Results

Blood cobalt ranged from undetectable to 3.20 μg/100 ml (median 0.10); urinary cobalt from 0.30 to 204.30 μg/g_creat (median 3.90) and long-term exposure to cobalt ranged from 0.15 to 6990.46 μg/g_creat·years (median 106.09). No effect of cobalt exposure on thyroid or red blood cell parameters was observed at these levels of exposure.

Conclusion

The results support the absence of effects on the thyroid and red blood cells when occupational exposure to cobalt is kept below the recommended biological limit of occupational exposure (15 μg Co/g_creat in urine).     

琥珀酸亚铁片对妊娠合并缺铁性贫血的疗效及血红蛋白、红细胞、血清铁蛋白的影响

目的观察琥珀酸亚铁片对妊娠合并缺铁性贫血(IDA)的治疗效果及其对血红蛋白(Hb)、红细胞(RBC)、血清铁蛋白(SF)的影响。方法选择我院2011年1月至2012年12月的妊娠合并缺铁性贫血患者120例(均符合入选标准),其中轻度贫血107例,中度贫血13例,重度贫血0例,给患者口服琥珀酸亚铁片,1²片/次,3次/d。分别测定治疗前后孕妇的Hb、RBC和SF,观察并记录实验过程中出现的不良反应,评价药物的安全性。结果 120例妊娠合并缺铁性贫血患者39例痊愈,57例显效,22例有效,2例无效,总有效率为98.3%。治疗后Hb、RBC和SF与治疗前比较差异有统计学意义(P<0.01)。治疗过程中部分患者出现轻微的不良反应,均未影响治疗效果。结论琥珀酸亚铁片对妊娠合并缺铁性贫血有显著的治疗效果,能明显提高妊娠合并缺铁性贫血患者的Hb、RBC和SF。     

Prostacyclin increases filterability of normal and rigidified human red blood cells in vitro

Red blood cell (RBC) deformability is a critical determinant of capillary flow. In a previous study we found decreased deformability (filterability) of red cells of patients with clinical symptoms of peripheral ischaemia associated with systemic sclerosis and prostacyclin (PGI2) infusion had beneficial effect on both the clinical symptoms and red cell filterability. The present study was therefore designed to investigate the effect of PGI2 on RBC deformability in vitro, by measuring the filterability of RBCs suspended in saline. The results demonstrate that PGI2 increases filterability of normal RBCs and significantly improves the impaired deformability of cells due to storage or calcium influx.     

The interactions of mesna and dimesna with the sulfate exchange in human red blood cells

The influence of disodium 2-mercaptoethane sulfonate disulfide (mesna, Uromitexan) and sodium 2-mercaptoethane sulfonate (dimesna) on the carrier mediated exchange of 35S-sulfate in human red blood cells was investigated in vitro in order to contribute to the understanding of pharmakokinetics and organospecific action of mesna. Countertransport indicated uptake of mesna in washed red blood cells by the carrier. In contrast, dimesna inhibited the transport of sulfate in a competitive manner. However, when 35S-sulfate uptake into red cells was studied with whole blood, addition of mesna was found to be inhibitory, which was caused by its rapid conversion to dimesna by plasma components. It is concluded that conversion of the anion carrier substrate mesna into the inhibitor dimesna is the reason that mesna or dimesna cannot be detected in red blood cells in vivo.