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The effects of sodium 2-mercaptoethane sulfonate (Mesna) on the mutagenicity of cyclophosphamide (CP) were assessed in vitro by the Ames test and in vivo in rats by analyzing micronuclei in bone marrow and mutagenic activity in urine. Mesna alone was negative in all test systems, while CP gave a positive response in all of them. In a combined treatment there was no significant reduction of the CP-induced mutagenicity in Salmonella. In rats the frequency of bone marrow micronuclei was not diminished when Mesna was given together with CP. May-Grunwald-Giemsa staining and Hoechst-Pyronin fluorescent staining techniques for micronuclei yielded similar results. The urine of rats treated with CP was mutagenic to Salmonella and no significant difference was observed when the rats had received both Mesna and CP. The results give support to the theory that Mesna acts primarily by reducing the toxicity of metabolites of CP, particularly acrolein, in the urinary tract and not by suppressing the mutagenicity of the active metabolites of CP.

Quinone metabolites of catechol estrogens have been postulated to mediate estradiol-induced carcinogenesis. In this study, this postulate was examined by investigating the effect of modulators of quinone metabolism on estradiol-induced tumor incidence in male Syrian hamsters. 2(3)-t-Butyl-4-hydroxyanisol (BHA) and dicumarol which are known to stimulate or inhibit respectively, the activity of quinone reductase, lowered tumor incidence by 33 and 42% respectively (3/9 and 5/12 tumor-free animals/total respectively), from 100% (13/13) observed with 17 beta-estradiol (E2) treatment only. Ebselen, a substance with glutathione peroxidase-like activity, and sodium 2-mercaptoethanesulfonate (Mesna), a cytoprotective thiol-containing agent, were only marginally effective in decreasing the estradiol-induced kidney tumor incidence (3/11 and 4/19 tumor-free animals/total respectively). The lowering of tumor incidence by BHA and dicumarol correlated well with a 40-45% decrease in renal peroxidatic activity of cytochrome P450 in hamsters treated with these substances plus estradiol for 1 month. In addition, these compounds also inhibited the oxidation of diethylstilbestrol to its corresponding quinone in vitro. An influence on quinone reductase or other detoxifying enzymes in chronically treated male Syrian hamsters could not be detected. These data support a mediation of estradiol-induced carcinogenesis by quinones formed by metabolic oxidation of catechol estrogens.

In 8 patients receiving intravenous isophosphamide 2 g/m2 at 2-week intervals for advanced bronchogenic carcinoma the protective effect of 2-mercaptoethane sulphonate sodium (mesnum) against isophosphamide-induced urothelial toxicity was tested in a single-blind crossover trial. With isophosphamide alone, 7 of the 8 patients developed either haematuria or symptoms of bladder irritation; when mesnum was given in addition, only 1 patient had microhaematuria and frequency, and this was in association with a urinary-tract infection. 5 patients then received fifteen courses of isophosphamide in increasing doses of 4 to 8 g/m2 i.v. with mesnum. In contrast to previous experience with isophosphamide at this high dosage, frank haematuria was never seen, microhaematuria was seen after only three courses, and mild dysuria after only one course. Pharmacokinetic studies showed that mesnum did not interfere with the metabolism of isophosphoramide or its active anti-tumour metabolite, isophosphoramide mustard. Mesnum therefore enhances the therapeutic ratio of isophosphamide and may thereby increase its clinical efficacy.

Mesna is a pharmacologically unremarkable, physiologically largely inert and almost totally non-toxic thio compound. It is rapidly eliminated renally and only slightly permeates into tissues. It has been shown experimentally that the bladder damage inducible in the rat by administration of oxazaphosphorine cytostatics can be successfully prevented by quite small doses of mesna. The detoxifying action of mesna is limited to the kidneys and the efferent urinary tract. The systemic effects of the oxazaphosphorines, however, remain unaffected. This applies particularly to the curative oncocidal efficacy of these compounds. It has also been shown experimentally that mesna does not affect the curative effects of other cytostatic drugs (doxorubicin, BCNU, methotrexate, vincristine). The efficacy of the cardiac glycoside proscillaridin is also not impaired by mesna.

Presumably the coadministration of the uroprotector mesna in cyclophosphamide treatment does not influence the systemic activity of its activated metabolite. This was newly investigated in a mouse model. The LD50 values of i.p. administered mafosfamide, a derivative of act. CP, were increased by the simultaneous i.p. administration of mesna (mafosfamide: mesna 1:2 on a molar weight basis) from 590 mg/kg to 750 mg/kg, and after i.v. injection of cytostatic and thiol from 505 mg/kg to 810 mg/kg. Administration of 2 X molar cysteine i.v. or i.p. to mafosfamide-treated animals was even more effective against its lethal toxicity (LD50 i.p. 1800 mg/kg and i.v. 1130 mg/kg). Bone marrow toxicity (severe leukocytopenia) was partially abolished by both thiols. Also the therapeutic efficacy of act. CP against L1210 leukemia in DBA2 mice was reduced by 50% in the presence of cysteine and of mesna. Compared with mesna the higher detoxification effect of cysteine is attributed to its longer half-life (t1/2 20 min vs 12 min of mesna) and presumably an accumulation of cysteine in some cell systems (distribution coefficient 1.20 ml/g vs 0.68 ml/g of mesna). Nevertheless, our study clearly demonstrates a distinct systemic deactivation of act. CP by mesna, which might be of clinical relevance.

The effect of the application of a single oral dose of 100 mg of three mucolytic agents (N-acetylcysteine, carbocysteine and Na-2-mercaptoethane sulphonate) on the ultrastructure of the tracheal epithelium of healthy rabbits was studied. Due to the function of oral mucolytics the goblet cells were overstimulated and injured. Na-2-mercaptoethane sulphonate was the least irritating substance. Acetylcysteine produced the most pronounced injury of the goblet cells, followed by rapid differentiation of these cells. Oral administration of all mucolytics studied caused local impairment of mucus flow in the airways.

Extracts of Methanosarcina barkeri reduced methanol and CO2 to CH4 in the presence of H2 and converted methanol stoichiometrically into CH4 and CO2 in the absence of H2. In dialyzed cell-free extracts these reactions were stimulated by 2-mercaptoethanesulfonic acid (coenzyme M) and some derivatives (acetyl and formylcoenzyme M and the oxidized form of coenzyme M), which could be converted to coenzyme M by enzyme systems present in the extracts. Methylcoenzyme M could not be used in these systems.

The chemotherapy of malignant tumors with oxazaphosphorine cytostatics, e.g., cyclophosphamide (CP) and ifosfamide, is limited by their severe urotoxic side effects. As a result of cytotoxic damage, the proliferation of the urinary bladder urothelium is considerably stimulated during an intensive reparative regeneration. The recently developed uroprotector sodium 2-mercaptoethane sulfonate (Mesna) allows regional detoxification limited to the kidneys and lower urinary tract and thus protects against damage by aggressive oxazaphosphorine metabolites. The object of the present quantitative autoradiographic investigation was to study urothelial proliferation in the bladder of rats after administration of CP alone and in combination with Mesna. 20 h after intraperitoneal injection of a single dose of CP alone (100 mg/kg), the urothelium showed a steep rise of the 3H-thymidine (3H-TdR) labeling index which reached a peak of 17.6% at 30 h. Thereafter, the 3H-TdR index rapidly dropped. A second peak of 4.4% was observed after 7 days. With supplementary intravenous administration of a single dose of Mesna (100 mg/kg) 15 min before treatment with CP, the labeling index was substantially lower than after administration of CP alone. Thus, maximal values of only 1.6 and 1.9% were observed at 35 h and 7 days, respectively. Histopathological examination of the bladders showed severe necrotizing and ulcerative cystitis, 10, 20 and 25 h after administration of CP alone whereas with additional treatment with Mesna only slight edema of the lamina propria developed. The results obtained clearly demonstrate the protective action of Mesna on the urothelium of the lower urinary tract against the urotoxic effects of CP.

The effect of some sulfhydryl compounds on the uptake of cytosine arabinoside (Ara-C) by normal and neoplastically transformed mouse thymus cells was studied. Sodium 2-mercaptoethanesulphonate (Mesna) was found to greatly inhibit (in 80%) the uptake of Ara-C by normal cells. Two other SH-compounds (cysteine and N-acetyl-cysteine) displayed no such effect. None of the three compounds reduced the uptake of Ara-C by neoplastic thymus cells. The possible pharmacological implications of these findings are discussed.

Cyclophosphamide (CP) is metabolized to the reactive intermediates, phosphoramide mustard (PAM) and acrolein (AC), which have generally different molecular binding targets. Sodium 2-mercaptoethanesulfonic acid (MESNA) has been used clinically to alleviate hemorrhagic cystitis caused by CP chemotherapy, has exhibited anticarcinogenic effects in rats exposed to CP during a long-term bioassay, and acts in the urogenital tract by reacting with 4'-OH-CP and AC. The purpose of this study was to: (a) compare the relative abilities of PAM and AC to induce cytogenetic damage and cytotoxicity in cultured human lymphocytes; (b) assess the efficacy of MESNA to attenuate the cytogenetic damage and cytotoxicity induced by CP, AC, PAM, and diethyl-4'-hydroperoxycyclophosphamide (DEHP-CP), an activated AC-generating compound; and (c) determine if concanavalin A-stimulated T-lymphocytes, which differentiate into suppressor cells upon lectin activation, exhibit any heightened cytogenetic sensitivity compared to a variety of cultured mammalian cells during exposure to PAM or AC as reported by other investigators. Purified mononuclear leukocytes were stimulated with concanavalin A and exposed to CP (0.5-2.0 mM) without an exogenous activation system, AC (0.001-40.0 microM), PAM (0.0014-27.1 microM), or DEHP-CP (0.1-100.0 microM) in the presence or absence of MESNA (1, 5, or 10 mM). All four compounds induced significant concentration-related increases in the SCE frequency, but only PAM was clastogenic. On an induced SCE/microM basis, PAM was about 130 and 193 times more potent than were DEHP-CP and AC, respectively. MESNA protected against the cytogenetic damage and cytotoxicity induced by the four compounds, but it was particularly effective against AC and DEHP-CP by abolishing SCE induction completely. SCEs and chromosome aberrations differed considerably in their induction kinetics in lymphocytes exposed to PAM, and these disparities suggested an uncoupling of the two phenomena. Although SCE induction was not consistently associated with cytotoxicity with the four agents, chromosome aberration induction coincided with an inhibition of cell cycle kinetics in PAM-treated cells. The exceptionally high SCE frequency of up to 21 times baseline in cells exposed to PAM indicates that T-suppressor lymphocytes stimulated with concanavalin A may be particularly sensitive to the DNA-damaging effects of PAM. Finally, these data suggest that the anticarcinogenicity of MESNA correlates with its ability to attenuate cytogenetic damage and cytotoxicity induced by reactive CP metabolites.

Fosfomycin and mesna were investigated in rats and mice concerning their detoxifying effects on cisplatin toxicity in comparison to sodium thiosulfate, a known protector against cisplatin nephrotoxicity. After separate i.p. injection of cisplatin and fosfomycin (500 mg/kg) or mesna (800 mg/kg) a slight increase in the 50% lethal dose of cisplatin was found in all animals. In mice sodium thiosulfate proved to be far more effective in preventing lethal toxicity and nephrotoxicity as measured by blood urea nitrogen increase. Fosfomycin and mesna were almost without influence on cisplatin treatment of L-1210 leukemia whereas their inhibition of the antitumor effect against S-180 ascites sarcoma (increase of in cisplatin dose to cure 50% of animals from 2.0 mg/kg to 3.5/4.7 mg/kg cisplatin) was similar to thiosulfate, which showed a strong inhibiting effect in the treatment of both tumors. In rats fosfomycin distinctively reduced the antitumor efficacy of cisplatin against Yoshida ascites sarcoma. Thus the concurrent injection of fosfomycin and mesna reduced both the toxicity and the antitumor activity of cisplatin. Therefore their simultaneous administration in addition to cisplatin via the same injection route should be avoided. Due to the weak detoxifying efficacy of fosfomycin and mesna they cannot be used instead of sodium thiosulfate for renal protection against cisplatin toxicity in local i.p. treatment modalities.

Glutathione (GSH, 1 mmol/l) inhibits Fe2+/ascorbic acid induced liver microsomal lipid peroxidation. Oxidized GSH (GSSG, 1 mmol/l) did not affect rate or extent of lipid peroxidation. The inhibition by GSH seems specific since the sulfhydryl agent sodium 2-mercaptoethanesulfonate (mesna) gave a slight stimulation of lipid peroxidation. This stimulation is probably explained by a reduction by mesna of dehydroascorbic acid which is formed during the incubation, into ascorbic acid. Remarkably, mesna (1 mmol/l) added together with GSSG (1 mmol/l) produced the same inhibition as with 1 mmol/l GSH alone. This can be explained by direct reduction of GSSG to GSH by mesna. This is corroborated in experiments in which GSH is measured directly. Dimesna did not show an effect on lipid peroxidation. In the protective action of mesna against reactive substances its ability to reduce GSSG should be appreciated.

The disintegrating effect of three reducing thiol derivatives: [sodium mercaptoethane sulphonate (Mesna), N-acetyl-L-cysteine (NAC) and dithio-1,4-threitol (DTT)] was investigated in vitro upon blood clots formed in the absence or in the presence of tracheobronchial secretions and compared with the effect of iso-osmotic saline solution. The amounts of haemoglobin released from the clots after 30 min incubation and the initial rates of haemoglobin release were compared for the different products at different concentrations. All three reducing agents showed some ability to disintegrate mixed clots to an extent depending on their concentration. After 30 min incubation, statistical analysis showed a highly significant difference in favour of Mesna at the three concentrations used, i.e. 0.1, 1.0 and 10 mmol/1. The initial rate of haemoglobin release in presence of Mesna was at all concentrations significantly higher than that of NAC or DTT. The effects on normal blood clots were much less pronounced. The effectiveness of Mesna in splitting up mixed blood and mucus clots in the management of patients who had inhaled blood is discussed.

The effects of mesna (sodium 2-mercaptoethane-sulfonate) on the frequency of sister chromatid exchange (SCE) and chromosomal aberrations were studied in PHA-stimulated lymphocytes in vitro. Our data give no evidence for either an increase of SCE or chromosomal aberrations and, thus, do not suggest a mutagenic or cancerogenic potential of this drug, when used clinically for the reduction of urotoxicity caused by oxazaphosphorine derivatives in cancer therapy. The possibility of a radioprotective effect of mesna could not be supported by the results obtained in this test system. However, there remained a slight comutagenic effect of mesna, if used together with irradiation, which should be taken into account when this drug is administered in the preparation of patients for bone marrow transplantation.

The effect of 2-mercaptoethane sulphonate (mesna) on the inhibition of the human MLR by 4-hydroxycyclophosphamide or azathioprine was studied. 4-Hydroxycyclophosphamide (34 microM) completely inhibited the MLR and this inhibition was unaffected by 122 microM of 2-mercaptoethane sulphonate or its disulphide. At high concentrations (mM) 2-mercaptoethane sulphonate inhibited the MLR reaching 85% at 24 mM. 2-Mercaptoethane sulphonate (15-122 microM) had no effect on azathioprine (36 microM) inhibition. The results of these in vitro studies suggest that 2-mercaptoethane sulphonate does not interfere with cyclophosphamide or azathioprine induced suppression of cellular immunity.

An experimental model was developed, in which urinary bladder cancer was induced by cyclophosphamide in rats, thus reproducing cyclophosphamide-induced urinary bladder carcinogenesis observed in humans. It was possible in this model to achieve a highly significant reduction of cyclophosphamide-induced urinary bladder cancer by concomitant administration of sodium 2-mercaptoethane sulfonate (mesna). A significant delay of urinary bladder carcinogenesis by administration of the uroprotective substance mesna was also observed when using butylbutanolnitrosamine for inducing urinary bladder cancer. It was thus for the first time possible to assure chemoprevention of this tumor type by administration of a specific antidote.

The in vitro activity against Pseudomonas aeruginosa was investigated for serial dilutions of eight anti-Pseudomonas antibiotics in combination with serial dilutions of N-acetylcysteine (NAC) and 2-mercaptoethane sulphonate (MES). The results indicated that addition of NAC and MES to the antibiotics increased the MIC values for tobramycin, netilmicin, piperacillin, azlocillin, cefsulodin, ceftazidime and imipenem but not for colistin. The decrease of MIC found in high concentrations of NAC and MES was probably due to the bacteriostatic effect of the drugs per se and not to synergism with the antibiotics.

We have studied the effects of the mucolytic thiol agent mercapto-ethanesulphonate (mesna) on the activity of both polymorphonuclear leucocyte (PMN) elastase and antileucoprotease in vitro. In all tests a specific synthetic substrate was used to measure elastase activity, which was then related to enzyme activity in the absence of mesna. The relative elastase activity decreased to 67.5% of control values after the enzyme had been incubated in a 120 mmol/l mesna solution. In the sol phase of purulent sputum, elastase activity decreased to 45% after the sol phase had been incubated in a 600 mmol/l mesna solution. The inability to reverse the inhibition of mesna by increasing the substrate concentration indicated that mesna acts as a non-competitive inhibitor of PMN elastase. Incubation of elastase with antileucoprotease reduced the relative elastase activity to 21%. When antileucoprotease was preincubated in a 60 mmol/l mesna solution under identical assay conditions, a relative elastase activity of 39% was observed. Inhibition experiments with mesna treated antileucoprotease, in which sulphydryl groups were blocked with iodoacetamide, strongly suggested that the dissociation constant (Ki) of the fraction of antileucoprotease that retains activity after the incubation with mesna was not changed. Elastase inhibitory activity in mucoid sol phase, which can be ascribed mainly to antileucoprotease, decreased to 53% after incubation with mesna at a concentration of 960 mmol/l. Incubation of PMN elastase/antileucoprotease complex with mesna did not result in any release of active PMN elastase from the antileucoprotease. It is concluded that mesna and other thiol compounds, when locally administered, may influence the proteinase-antiproteinase balance in the airways by their effect on both PMN elastase and antileucoprotease.

The possible protective action of sodium-2-mercaptoethanesulfonate (mesna) on hemotoxicity induced by anticancer drugs was tested in normal mice. Mesna (100 mg/kg b.w.) was injected i.v. 1 h before the i.v. administration of cyclophosphamide (10, 120, and 200 mg/kg b.w.), doxorubicin (4.32, 7.2, and 12 mg/kg b.w.) and cis-diamminedichloroplatinum (5.4, 9, and 15 mg/kg b.w.). Results show that in this experimental model mesna does not seem to protect against toxicity of the tested anticancer drug on hemopoietic progenitor cells.

Certain deleterious effects of cyclophosphamide, for example urotoxicity, can be prevented by the administration of thiol compounds such as 2-mercaptoethane sulfonate (MESNA) without altering the therapeutic efficacy of cyclophosphamide. To evaluate the effect of MESNA on the teratogenicity of cyclophosphamide, pregnant Sprague-Dawley rats were divided into nine treatment groups. Individual groups were administered 0.9% NaCl or cyclophosphamide (10 or 15 mg/kg) alone or in combination with MESNA at one of two doses (5 or 30 mg/kg) on Day 13 of gestation. The fetuses were examined for malformations on Day 20 of gestation. Cyclophosphamide alone produced malformations in 50% (10 mg/kg) or 100% (15 mg/kg) of the fetuses. The abnormalities observed were hydrocephaly, hind- and forelimb defects, open eyes, cleft palate, edema, micrognathia, omphalocele, and various skeletal defects. MESNA alone did not induce a significant number of fetal malformations compared to control. The low dose of MESNA had no significant effect on the total incidence of external malformations produced by either dose of cyclophosphamide. The high dose of MESNA significantly reduced the total number of externally abnormal fetuses and fetuses with skeletal defects produced by both 10 and 15 mg/kg of cyclophosphamide. This protection, although statistically significant (p less than or equal to 0.05), is probably not extensive enough for MESNA to be considered effective in protecting pregnant women from the teratogenic effects of cyclophosphamide chemotherapy.

The action of arginine 2-mercaptoethane sulfonate in comparison with sodium 2-mercaptoethane sulfonate on cell growth and cell adhesion of a metastatic sub-line of murine melanoma (F10/B16) was investigated. The capability of the two compounds to interfere with the cytotoxicity of 4-hydroperoxycyclophosphamide and of cis-dichlorodiammineplatinum(II) in F10 cells was studied. The in vivo studies included the determination of acute and sub-acute toxicity of the two salts on mice. Very low toxicity and no significant differences between the two compounds were detected.

The interactions between mercaptoethanesulphonic acid (mesna) and transition metal ions was investigated. Mesna was shown to react with selected transition metals (to form covalent metal thiol compounds) resulting in reduction of their oxidation state with the possible concomitant oxidation of mesna to dimesna. The reactions between mesna and copper were investigated in detail. Mesna is known to bind to serum albumin, copper was found to chemically combine with the mesna protein complex. Administration of copper to rats resulted in accumulation of copper in the kidney, while simultaneous administration of mesna and copper resulted in accumulation of copper in liver. The possible role of mesna-albumin complexes in copper transport is postulated and the importance of this in cancer treatment, where serum copper levels are often raised, is discussed.

Since the usefulness of high-dose cyclophosphamide is often limited by hemorrhagic cystitis, and the use of sulfhydryl-containing compounds prevents this side effect, this study was carried out to compare the uroprotective efficacy of 2-mercaptoethane sulfonate (MESNA) with that of reduced glutathione. In experimentally cyclophosphamide-induced urotoxicity in mice, the protective efficacy and potency of these thiols were similar, since both agents afforded complete protection in the same dose range. This finding suggests that these compounds are suitable sources of urinary thiols. Although the rationale for the clinical use of these protectors is similar, glutathione may have therapeutic advantages over MESNA because of a wider margin of safety and multiple protective actions displayed by the tripeptide thiol.

One of the serious toxicities of cyclophosphamide chemotherapy is urotoxicity. In addition to causing leukopenia, high-dose cyclophosphamide caused both depression of hepatic microsomal enzyme activities and extensive urinary bladder damage, suggesting that a common biochemical mechanism may be responsible for both of these effects. Administration of 180 or 200 mg cyclophosphamide per kg to Wistar rats caused 41 to 67% decrease in aryl hydrocarbon hydroxylase activity, a 21 to 54% decrease in aminopyrine demethylase activity, and a 34 to 40% decrease in cytochrome P-450 content. This dose of cyclophosphamide also caused hematuria as well as necrosis and edema in the urinary bladder. Administration of N-acetylcysteine or sodium-2-mercaptoethane sulfonate (mesnum) with cyclophosphamide, while not protecting against leukopenia, protected against the enzymatic inactivation and urotoxicity. The biochemical basis of these observations is discussed. The results suggest that a common metabolite of cyclophosphamide, most probably acrolein, is responsible for both of these undesirable effects of cyclophosphamide therapy. Use of combinations including cyclophosphamide and an appropriate thiol may increase the therapeutic index of this drug.

Cyclophosphamide is an effective antitumor agent with considerable side effects such as urotoxicity and carcinogenicity. These negative attributes may be caused by toxic and genotoxic metabolites, respectively. Mesna (sodium 2-mercaptoethane sulfonate) decreases the urotoxicity by scavenging the toxic metabolite acrolein. The present study was aimed at elucidating whether a similar scavenging of genotoxic alkylating intermediates could be found, which might cause the reduction in carcinogenicity. In vitro studies on the genotoxic and toxic properties of cyclophosphamide and its major metabolites to bacteria were therefore performed in the presence of Mesna. Mesna did not reduce the mutagenicity of any of the tested metabolites. Mesna clearly inhibited the toxic properties of acrolein. After in vivo application of Mesna and cyclophosphamide to rats, however, a lower yield of mutagens in the excreted urine was observed than after application of cyclophosphamide only.

Urotoxic side effects, especially hemorrhagic cystitis, have so far been a limiting factor in the therapeutic use of cyclophosphamide (Endoxan), ifosfamide (Holoxan), and trofosfamide (Ixoten). The uroprotective agent mesna (Uromitexan) allows regional detoxification in the kidney and the urinary tract, and thus clinical prevention of the urotoxic side effects of the above cytostatics. The uroprotective mechanism of mesna is based on the formation of nontoxic additive compounds with acrolein and 4-hydroxy-metabolites. In the body, mesna is rapidly transformed into its biologically inert disulfide. After glomerular filtration mesna disulfide is rapidly reduced by reacting with the glutathion system and elimination in the urine as a free thiol compound, further detoxifying the aggressive oxazaphosphorine metabolites.

Sodium 2-mercaptoethane sulfonate (mesna, Uromitexan) is oxidized in the organism of rats to 2,2'-dithiodi-(ethane sodium sulfonate) (dimesna). Dimesna is partially reduced to the mercapto compound mesna (kidneys); both compounds are eliminated via the urine. Even after administration of dimesna mesna can be detected in the urine. Accordingly dimesna also proved to be an effective antidote against the urotoxic actions of cyclophosphamide and ifosfamide.

1 The efficacy of a mucolytic agent, 2-mercapto-ethane sulphonate, administered in the form of an aerosol was evaluated in a group of eleven patients with chronic bronchitis in a controlled, double-blind, crossover study. 2 Saline aerosol isotonic (1.21M, 7.1%) to the drug was used as a placebo. 3 Approximately 1 ml drug/placebo was inhaled by the patients twice a day for 3 days and a final dose was given on the mornings of the drug/placebo trial runs. 4 There was no improvement in this group of patients in lung function or subjective well being attributable to the drug. 5 The viscosity of sputum, dry macromolecular weight and N-acetyl neuraminic acid/fucose ratio remained unaltered throughout the study. 6 An enhancement of tracheobronchial clearance was obtained following the administration of either placebo (31%) or drug aerosols (24%) Statistical significance (P less than 0.01) was only achieved for the placebo and was attributed to an increase in sputum volume.

Although mesna afforded protection against the cytotoxicity of cisplatin in Chinese hamster cells, line V-79-753B, in vitro, there was no evidence for protection against nephrotoxicity when this drug combination was examined in the rat. It seems likely that cisplatin-induced nephrotoxicity is mediated by intracellular events in kidney cells which cannot be inhibited by mesna possibly due to its presence within cells in vivo as the stable and unreactive disulphide. On the basis of these data it is unlikely that combinations of mesna and cisplatin will be of therapeutic benefit in man.

Cyclophosphamide (100 mg/kg i.p.) produces severe bladder lesions in rats and induces an intense regeneration of the urothelium which can be followed up by 3H-thymidine incorporation. Simultaneously administered mesna (100 mg/kg i.v.) prevents these bladder lesions and no increased regeneration with 3H-thymidine incorporation can be observed.

This study describes the prolonged survival of male SD-rats that bear bladder carcinomas induced either with 44 mg/kg or 28 mg/kg of N-nitroso-N-butyl-N-(4-hydroxybutyl)amine (BBNOH), when daily doses of 350 mg/kg of sodium-2-mercaptoethane sulfonate (mesna) were administered concomitantly. The difference to carcinogen-treated positive controls was highly significant (P = 0.0009 and 0.0013, respectively). Tumor volumes at time of death (P less than 0.005) and frequency of metastases were also reduced in rats that received both compounds in comparison to BBNOH-treated animals.

cis-Diamminedichloroplatinum (cis-platinum) is an effective and widely used antitumor drug. Patients receiving cis-platinum, however, experience very profound and long lasting gastrointestinal symptoms. The role of intestinal mucosal toxicity in the pathogenesis of these symptoms is unclear. In this study we have investigated the thiol-containing compound mesna (sodium-2-mercaptoethanesulfonate) as a potential antidote to cis-platinum-induced gastrointestinal tract damage. In mice, mesna caused a significant reduction in the gastrointestinal toxicity of cis-platinum assessed by electron microscopy, villus recovery rate, and by disaccharidase estimations. Mesna also significantly reduced serum creatinine levels following cis-platinum. Administration of mesna prior (or immediately following) a 67% lethal dose of cis-platinum protected 87-100% of the animals from the lethal effects. The antitumor efficacy of cis-platinum in L1210 leukemia bearing mice was not affected by coadministration of mesna indicating that the protective effect may be tissue specific. In addition this finding indicates that mesna has potential as an agent which may improve the therapeutic index of cis-platinum in clinical practice.

In a preliminary experiment the wet weight of the rat urinary bladder appeared to correlate with cyclophosphamide toxicity. The effect of a proposed antidote (SMES), given on various time schedules, was studied using the wet weight as a measure of toxicity. At a cose of 20 mg/kg/SMES it was found to neutralize the toxicity of 100 mg cytoxan only when given simultaneously. It is suggested that this model might be used in further studies.

Urotoxic side effects, particularly haemorrhagic cystitis, have been a limiting factor for the therapeutic use of the oxazaphosphorine cytostatics cyclophosphamide, ifosfamide and trofosfamide. The development of mesna (Uromitexan) has made it possible to carry out regional detoxification in the kidneys and the efferent urinary tract and thus to achieve clinically prophylaxis against the urotoxic side effects of oxazaphosphorines. In the body, mesna is rapidly converted to the biologically inactive disulfide form (dimesna). After glomerular filtration, dimesna is reduced by interaction with the glutathione system of the renal tubular cells and is excreted in the urine as mesna, the free thiol compound. This compound is then capable of definitively detoxifying the oxazaphosphorine metabolites in the urine. In extensive experiments on rats, it has been demonstrated that the cyclophosphamide-induced occurrence of urinary bladder tumours could be reduced or even eliminated by simultaneous administration of mesna. Detoxification by mesna enables the clinical use of higher doses and, consequently, a possible increase in therapeutic efficiency.

The mucolytic drug Mistabron is often used in bleeding situations. The purpose of this study is to assess the safety of this drug in such circumstances. The platelet function of human blood is not impaired by clinically used Mistabron dosage, after stimulation with epinephrine, ADP or arachidonic acid. Coagulation proteins are not modified by Mesna, neither in vitro (blood from human beings), nor in vivo (rats).

The specificity of the growth requirement of Methanobacterium ruminantium strain M1 for a new coenzyme, 2-mercaptoethanesulfonic acid (HS--CoM), was examined. A variety of derivatives, analogs, and potential biosynthetic precursors of coenzyme M were tested; only a restricted range of thioether, thioester, and thiocarbonate derivatives of the cofactor were found to replace the HS--CoM requirement. Bromoethanesulfonic acid (BrCH2CH2SO3-), a halogenated analog of HS--CoM, potently inhibited the growth response. No coenzyme was detectable in a wide range of nonmethanogenic eucaryotic tissues and procaryotic organisms. However, all methanogens available in pure culture exhibited high levels of coenzyme M which ranged from 0.3 to 16 nmol/mg of dry weight.