Role of taurine in regulation of intracellular calcium level and neuroprotective function in cultured neurons

Glutamate-induced excitotoxicity has been implicated as an important mechanism underlying a variety of brain injuries and neurodegenerative diseases. Previously we have shown that taurine has protective effects against glutamate-induced neuronal injury in cultured neurons. Here we propose that the primary underlying mechanism of the neuroprotective function of taurine is due to its action in preventing or reducing glutamate-induced elevation of intracellular free calcium, [Ca(2+)](i). This hypothesis is supported by the following findings. First, taurine transport inhibitors, e.g., guanidinoethyl sulfonate and beta-alanine, have no effect on taurine's neuroprotective function, suggesting that taurine protects against glutamate-induced neuronal damage through its action on the extracellular membranes. Second, glutamate-induced elevation of [Ca(2+)](i) is reduced to the basal level upon addition of taurine. Third, pretreatment of cultured neurons with taurine prevents or greatly suppresses the elevation of [Ca(2+)](i) induced by glutamate. Furthermore, taurine was found to inhibit the influx but not the efflux of (45)Ca(2+) in cultured neurons. Taurine has little effect on the binding of [(3)H]glutamate to the agonist binding site and of [(3)H]MDL 105,519 to the glycine binding site of the N-methyl-D-aspartic acid receptors, suggesting that taurine inhibits (45)Ca(2+) influx through other mechanisms, including its inhibitory effect on the reverse mode of the Na(+)/Ca(2+) exchangers (Wu et al. [2000] In: Taurine 4: taurine and excitable tissues. New York: Kluwer Academic/Plenum Publishers. p 35-44) rather than serving as an antagonist to the N-methyl-D-aspartic acid receptors.

Neurotoxic effect of acamprosate, n-acetyl-homotaurine, in cultured neurons

Acamprosate (AC), N-acetyl-homotaurine, has recently been introduced for treating alcohol craving and reducing relapses in weaned alcoholics. AC may exert its action through the taurine system rather than the glutamatergic or GABAergic system. This conclusion is based on the observations that AC strongly inhibits the binding of taurine to taurine receptors while it has little effect on the binding of glutamate to glutamate receptors or muscimol to GABA(A) receptors. In addition, AC was found to be neurotoxic, at least in neuronal cultures, triggering neuronal damage at 1 mM. The underlying mechanism of AC-induced neuronal injury appears to be due to its action in increasing the intracellular calcium level, [Ca2+](i). Both AC-induced neurotoxicity and elevation of [Ca2+](i) can be prevented by taurine suggesting that AC may exert its effect through its antagonistic interaction with taurine receptors.

S-methyl-N,N-diethylthiocarbamate sulfoxide elicits neuroprotective effect against N-methyl-D-aspartate receptor-mediated neurotoxicity

Glutamatergic neurotransmission, particularly of the NMDA receptor type, has been implicated in the excitotoxic response to several external and internal stimuli. In the present investigation, we report that S-methyl-N,N-diethylthiocarbamate sulfoxide (DETC-MeSO) selectively and specifically blocks the NMDA receptor subtype of the glutamate receptors, and attenuates glutamate-induced neurotoxicity in rat-cultured primary neurons. Other major ionotropic glutamate receptor subtypes, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainate, were insensitive to DETC-MeSO both in vitro and in vivo. Disulfiram, the parent compound of DETC-MeSO, also inhibits glutamate receptors partially in vivo; however, it fails to inhibit glutamate receptors in mice pretreated with N-butyl imidazole, a cytochrome P450 enzyme inhibitor, implicating the need for bioactivation of disulfiram to be an effective antagonist. We showed that glutamate-induced increase in (45)Ca2+ was attenuated in rat-cultured primary neurons following pretreatment with DETC-MeSO. The Ca2+ influx into primary neurons, studied by confocal microscopy of the fluorescent Ca2+ dye fura-2, demonstrated a complete attenuation of NMDA-induced Ca2+ influx. Similarly, DETC-MeSO attenuated NMDA-induced (45)Ca2+ uptake. Glutamate-induced (45)Ca2+ uptake and Ca2+ influx, however, were partially blocked by DETC-MeSO, and this is consistent with both in vitro and in vivo studies in which DETC-MeSO partially blocked mouse brain glutamate receptors. In addition, DETC-MeSO pretreatment effectively prevented seizures in mice induced either by NMDA, ammonium acetate, or ethanol-induced kindling seizures, all of which are believed to be mediated by NMDA receptors. These data demonstrate that DETC-MeSO produces the neuroprotective effect through antagonism of NMDA receptors in vivo.

Identification of the human P-450 enzymes responsible for the sulfoxidation and thiono-oxidation of diethyldithiocarbamate methyl ester: role of P-450 enzymes in disulfiram bioactivation

Diethyldithiocarbamate methyl ester (DDTC-Me) is a precursorto the formation of S-methyl-N,N-diethylthiolcarbamate sulfoxide, the active metabolite proposed to be responsible for the alcohol deterrent effects of disulfiram. The present study investigated the role of human cytochrome P-450 (CYP) enzymes in sulfoxidation and thiono-oxidation of DDTC-Me, intermediary steps in the activation of disulfiram. Several approaches were used in an attempt to delineate the particular P-450 enzyme(s) involved in the sulfoxidation and thiono-oxidation of DDTC-Me. These approaches included the use of cDNA-expressed human P-450 enzymes, correlation analysis with sample-to-sample variation in human P-450 enzymes in a bank of human liver microsomes, and chemical and antibody inhibition studies. Multiple human P-450 enzymes (CYP3A4, CYP1A2, CYP2A6, and CYP2D6) catalyzed the sulfoxidation of DDTC-Me, as determined with cDNA-expressed enzymes. Several lines of evidence suggest that the sulfoxidation of DDTC-Me by human liver microsomes is primarily catalyzed by CYP3A4/5, including (1) a high correlation between DDTC-Me sulfoxidation and testosterone 6beta-hydroxylation; (2) increased DDTC-Me sulfoxidation in the presence of alpha-naphthoflavone, an activator of CYP3A enzymes; (3) inhibition of this reaction by inhibitors of CYP3A4/5 enzymes, such as troleandomycin and ketoconazole; and (4) inhibition of DDTC-Me sulfoxidation by antibodies against CYP3A enzymes. On the other hand, several lines of evidence suggested that the thiono-oxidation of DDTC-Me by human liver microsomes is catalyzed in part by CYP1A2, CYP2B6, CYP2E1, and CYP3A4/5, including (1) these human P450 enzymes among others have the capacity to catalyze this reaction, as determined with cDNA-expressed enzymes; (2) a high correlation between DDTC-Me thiono-oxidation and testosterone 6beta-hydroxylation, weak inhibition by ketoconazole, troleandomycin, and anti-CYP3A antibodies suggested a minor role for CYP3A4; (3) a high correlation with immunoreactive CYP2B6 suggested involvement of this enzyme; (4) weak inhibition of DDTC-Me thiono-oxidation by furafylline and anti-CYP1A antibody suggested involvement of CYP1A2; and (5) inhibition of DDTC-Me thiono-oxidation by DDTC and anti-CYP2E antibodies suggested a role for CYP2E1. Collectively, these data suggested CYP3A4/5 enzymes are the major contributors to the sulfoxidation of DDTC-Me by human liver microsomes, and CYP1A2, CYP2B6, CYP2E1, and CYP3A4/5 contribute toward DDTC-Me thiono-oxidation by human liver microsomes. This study, in conjunction with others (Madan et al., Drug Metab. Dispos. 23:1153-1162, 1995), may help explain the variability in disulfiram's effectiveness as an alcohol deterrent.

Regulation of taurine biosynthesis and its physiological significance in the brain

Cysteine sulfinic acid decarboxylase (CSAD), the rate-limiting enzyme in taurine biosynthesis, was found to be activated under conditions that favor protein phosphorylation and inactivated under conditions favoring protein dephosphorylation. Direct incorporation of 32P into purified CSAD has been demonstrated with [gamma 32P]ATP and PKC, but not PKA. In addition, the 32P labeling of CSAD was inhibited by PKC inhibitors suggesting that PKC is responsible for phosphorylation of CSAD in the brain. Okadaic acid had no effect on CSAD activity at 10 microM suggesting that protein phosphatase-2C (PrP-2C) might be involved in the dephosphorylation of CSAD. Furthermore, it was found that either glutamate- or high K(+)-induced depolarization increased CSAD activity as well as 32P-incorporation into CSAD in neuronal cultures, supporting the notion that the CSAD activity is endogenously regulated by protein phosphorylation in the brain. A model to link neuronal excitation, phosphorylation of CSAD and increase in taurine biosynthesis is proposed.

Glutathione carbamoylation with S-methyl N,N-diethylthiolcarbamate sulfoxide and sulfone. Mitochondrial low Km aldehyde dehydrogenase inhibition and implications for its alcohol-deterrent action

S-Methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) and sulfone (DETC-MeSO2) both inhibit rat liver low Km aldehyde dehydrogenase (ALDH2) in vitro and in vivo (Nagendra et al., Biochem Pharmacol 47: 1465-1467, 1994). DETC-MeSO has been shown to be a metabolite of disulfiram, but DETC-MeSO2 has not. Studies were carried out to further investigate the inhibition of ALDH2 by DETC-MeSO and DETC-MeSO2. In an in vitro system containing hydrogen peroxide and horseradish peroxidase, the rate of DETC-MeSO oxidation corresponded to the rate of DETC-MeSO2 formation. Carbamoylation of GSH by both DETC-MeSO and DETC-MeSO2 was observed in a rat liver S9 fraction. Carbamoylation of GSH was not observed in the presence of N-methylmaleimide. In in vitro studies, DETC-MeSO and DETC-MeSO2 were equipotent ALDH2 inhibitors when solubilized mitochondria were used, but DETC-MeSO was approximately four times more potent than DETC-MeSO2 in intact mitochondria. In studies with rats, the dose (i.p. or oral) required to inhibit 50% ALDH2 (ED50) was 3.5 mg/kg for DETC-MeSO and approximately 35 mg/kg for DETC-MeSO2, approximately a 10-fold difference. Furthermore, maximum ALDH2 inhibition occurred 1 hr after DET(-MeSO administration, whereas maximal ALDH2 inhibition occurred 8 hr after DETC-MeSO2 dosing. DETC-MeSO is, therefore, not only a more potent ALDH2 inhibitor than DETC-MeSO2 in vivo, but also in vitro when intact mitochondria are utilized. The in vitro results thus support the in vivo findings. Since oxidation of DETC-MeSO can occur both enzymatically and non-enzymatically, it is possible that DETC-MeSO2 is formed in vivo. DETC-MeSO2, however, is not as effective as DETC-MeSO in inhibiting ALDH2, probably because it has difficulty penetrating the mitochondrial membrane. Thus, even if DETC-MeSO2 is formed in vivo from DETC-MeSO, it is the metabolite DETC-MeSO that is most likely responsible for the inhibition of ALDH2 after disulfiram administration.

Carbamoylation of brain glutamate receptors by a disulfiram metabolite

S-Methyl-N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO), a metabolite of the drug disulfiram, is a selective carbamoylating agent for sulfhydryl groups. Treatment of glutamate receptors isolated from mouse brain with DETC-MeSO blocks glutamate binding. In vivo, carbamoylated glutathione, administered directly to mice or formed by reaction of DETC-MeSO with glutathione in the blood, also blocks brain glutamate receptors. Carbamoyl groups appear to be delivered to brain glutamate receptors or to liver aldehyde dehydrogenase in vivo by a novel glutathione-mediated mechanism. Seizures caused by the glutamate analogs N-methyl-D-aspartate and methionine sulfoximine, or by hyperbaric oxygen, are prevented by DETC-MeSO, indicating that carbamoylation of glutamate receptors gives an antagonist effect. These observations offer an explanation for some of the previously reported neurological effects of disulfiram, such as its ability to prevent O2-induced seizures. Furthermore, some of the physiology of the disulfiram-ethanol reaction, that could not be accounted for based on the known inhibition of aldehyde dehydrogenase alone, may be explained by disulfiram's effect on glutamate receptors.

Protein phosphorylation and taurine biosynthesis in vivo and in vitro

Taurine is known to be involved in many important physiological functions. Here we report that both in vivo and in vitro the taurine-synthesizing enzyme in the brain, namely cysteine sulfinic acid decarboxylase (CSAD), is activated when phosphorylated and inhibited when dephosphorylated. Furthermore, protein kinase C and protein phosphatase 2C have been identified as the enzymes responsible for phosphorylation and dephosphorylation of CSAD, respectively. In addition, the effect of neuronal depolarization on CSAD activity and 32P incorporation into CSAD in neuronal cultures is also included. A model to link neuronal excitation and CSAD activation by a Ca2+-dependent protein kinase is proposed.

Identification of the human and rat P450 enzymes responsible for the sulfoxidation of S-methyl N,N-diethylthiolcarbamate (DETC-ME). The terminal step in the bioactivation of disulfiram

The present study investigated the role of rat and human cytochrome P450 enzymes in the sulfoxidation of S-methyl N,N-diethylthiolcarbamate (DETC-Me) to S-methyl N,N-diathylthiolcarbamate sulfoxide (DETC-Me sulfoxide), the putative active metabolite of disulfiram. DETC-Me sulfoxidation by microsomes from male and female rats treated with various cytochrome P450-enzyme inducers suggested that multiple enzymes can catalyze this reaction, and these include, CYP1A1/2, CYP2B1/2, and CYP3A1/2. All cDNA-expressed human cytochrome P450 enzymes examined catalyzed the sulfoxidation of DETC-Me. The turnover rates (min-1) of DETC-Me sulfoxidation by the cDNA-expressed cytochrome P450 enzymes ranked as follows: CYP3A4 > CYP2A6 = CYP2C9 > CYP1A2 > CYP2B6 = CYP2E1 > CYP1A1 > CYP2D6. Interestingly, CYP3A4 ranked first or last, depending on whether or not additional NADPH-cytochrome P450 reductase was coexpressed in the lymphoblastoid cells. This complicated estimates of the contribution of CYP3A4 to DETC-Me sulfoxidation by human liver microsomes. The sample-to-sample variation in DETC-Me sulfoxidation by bank of human liver microsomes (N=13) correlated highly with coumarin 7-hydroxylation (r=0.88) and testosterone 6beta-hydroxylation (r=0.90), suggesting that CYP2A6 and CYP3A4/5 contribute to the sulfoxidation of DETC-Me by human liver microsomes. Although, chlorzoxazone 6-hydroxylation (a marker for CYP2E1) correlated poorly with DETC-Me sulfoxidation, the correlation improved from r=0.07 to r=0.44 when DETC-Me sulfoxidation was studied in the presence of the CYP2A6 inhibitor, coumarin. Similarly, when DETC-Me sulfoxidation was studied in the presence of diethyldithiocarbamate (DDTC), the inhibited DETC-Me sulfoxidase activity correlated better (r=0.50) with chlorzoxazone 6-hydroxylase, compared with DETC-Me sulfoxidase activity in the absence of DDTC (r=0.09). Polyclonal antibodies against CYP2E1 caused a modest inhibition (30%) of DETC-Me sulfoxidation by human liver microsomes. Anti-CYP3A1 antibodies completely inhibited DETC-Me sulfoxidation by cDNA-expressed CYP3A4. Under similar conditions, DETC-Me sulfoxidation by human liver microsomes was only partially inhibited by anti-CYP3A1 antibodies. Although studies with the rat and cDNA-expressed cytochrome P450 enzymes suggested that CYP1A2 contributed to DETC-Me sulfoxidation, this reaction was not inhibited by either furafylline ( a mechanism-based inhibitor of CYP1A2) or antibodies against CYP1A1/2. A significant role for CYP2C9 was excluded by the inability of sulfaphenazole to inhibit the sulfoxidation of DETC-Me by human liver microsomes. Collectively, these data suggest that multiple cytochrome P450 enzymes can catalyze the sulfoxidation of DETC-Me. In human liver microsomes the CYP2A6, CYP2E1, and CYP3A4/5 all contribute significantly to the sulfoxidation of DETC-Me. It is interesting to note that DDTC, the reduced metabolite of disulfiram, is known to inhibit these same enzymes. The ability of DDTC to block the formation of DETC-Me sulfoxide may explain why the dose of disulfiram required to produce a disulfiram-ethanol reaction in alcoholics is so variable and often inadequate.

Characterization of diethyldithiocarbamate methyl ester sulfine as an intermediate in the bioactivation of disulfiram

Disulfiram is bioactivated through a series of intermediates, ultimately forming S-methyl-N,N-diethylthiolcarbamate sulfoxide (DETC-Me sulfoxide), the metabolite proposed to be responsible for the in vivo inhibition of rat liver mitochondrial low Km aldehyde dehydrogenase (ALDH2). Diethyldithiocarbamate methyl ester sulfine (DDTC-Me sulfine) also has been recently identified as a possible metabolite of disulfiram (Madan and Faiman, 1994). In the present studies, DDTC-Me sulfine was characterized and was found to inhibit ALDH2 in vivo (ID50 = 57 mumol/kg) but not in vitro. Maximum inhibition of ALDH2 in rats was observed 1 hr after the i.p. administration of DDTC-Me sulfine. Pretreatment of rats with 1-benzylimidazole, a cytochrome P450 inhibitor, blocked the DDTC-Me sulfine-mediated inhibition of ALDH2. This suggested that DDTC-Me sulfine was further bioactivated by a cytochrome P450-dependent mechanism. DDTC-Me sulfine could not be detected in rat plasma after the i.p. administration of disulfiram (75 mg/kg), DDTC-Me (122 mg/kg) or DDTC-Me sulfine (22.6 mg/kg). However, S-methyl N,N-diethylthiolcarbamate (DETC-Me), the desulfurated form of DDTC-Me, was detected as a major metabolite of DDTC-Me sulfine in rat plasma after DDTC-Me sulfine administration. Also, a disulfiram-like-ethanol reaction was observed in rats treated with DDTC-Me sulfine and challenged with ethanol. These data provided additional support for the idea that DDTC-Me sulfine is an intermediate formed after DDTC-Me metabolism and is probably a precursor to DETC-Me in the overall bioactivation of disulfiram to DETC-Me sulfoxide.

Inhibition of rat liver low Km aldehyde dehydrogenase by thiocarbamate herbicides. Occupational implications

S-Methyl N,N-diethylthiolcarbamate (DETC-Me) is a metabolite formed during the bioactivation of disulfiram. The formation of its corresponding sulfoxide, S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO), from DETC-Me is required for low Km mitochondrial aldehyde dehydrogenase (ALDH2, EC 1.2.1.3) inhibition. DETC-Me is similar in structure to thiocarbamate herbicides with the general structure R1R2NC(O)SR3. Representative herbicides studied were n-propyl, n-propylthiocarbamate ethyl ester (EPTC), molinate, vernolate, ethiolate and butylate. All of these thiocarbamate herbicides inhibited rat liver ALDH2 in vivo. The dose of these thiocarbamates that inhibited rat liver ALDH2 by 50% (ID50) when administered 8 hr before determination of ALDH2, was found to be 5.2, 3.1, 1.6, 12, and 174 mg/kg, respectively. These thiocarbamates were ineffective rat liver ALDH2 inhibitors in vitro, unless rat liver microsomes and an NADPH-generating system were added to the incubation. The respective thiocarbamate sulfoxides were formed when the thiocarbamates were incubated with liver microsomes and an NADPH-generating system. The thiocarbamate sulfoxides all inhibited rat liver ALDH2 in vitro. An equimolar dose of molinate and molinate sulfoxide inhibited rat liver ALDH2 in vivo to the same degree. Molinate-treated rats challenged with ethanol exhibited a disulfiram-like ethanol reaction. In conclusion, thiocarbamate herbicides inhibit ALDH2, probably due to the formation of their sulfoxide, and therefore have the potential to produce a disulfiram-like ethanol reaction in an unsuspecting population.

Glutathione- and glutathione-S-transferase-dependent oxidative desulfuration of the thione xenobiotic diethyldithiocarbamate methyl ester

Oxidative desulfuration of diethyldithiocarbamate methyl ester (DDTC-Me), a thione xenobiotic and a metabolite of disulfiram, was studied. Using a rat liver microsomal incubation system, DDTC-Me was oxidized at the thionosulfur group, forming DDTC-Me sulfine. Only minimal desulfuration of DDTC-Me to S-methyl-N,N-diethylthiolcarbamate (DETC-Me) occurred. Desulfuration of DDTC-Me increased 4-fold when the microsomal incubation was supplemented with reduced glutathione (GSH) and increased 8-fold when both GSH and glutathione-S-transferase (EC 2.5.1.18) were added. Similar results were obtained using a simplified system containing DDTC-Me sulfine, GSH, and glutathione-S-transferase. This suggested that DDTC-Me sulfine is a stable intermediate formed before DDTC-Me is desulfurated to DETC-Me. This unprecedented desulfuration process can be explained as follows. GSH attacks the oxithiirane isomer of DDTC-Me sulfine, resulting in ring opening followed by loss of glutathione hydrodisulfide, which is reduced by GSH to oxidized glutathione and H2S. GSH can also reduce DDTC-Me sulfine to DDTC-Me. This mechanism is supported by in vitro studies. An approximately 1:1 stoichiometry was observed for the formation of H2S and DETC-Me. A 1:1 stoichiometry was also observed for the consumption of DDTC-Me sulfine, formation of DETC-Me plus DDTC-Me, and formation of oxidized glutathione. Glutathione hydrodisulfide was trapped by derivatization in situ using 4-vinylpyridine. Oxidative desulfuration of a series of dithiocarbamate esters also followed a similar mechanism.

Diethyldithiocarbamate methyl ester sulfoxide, an inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase and putative metabolite of disulfiram

S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) is a potent inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase (ALDH2) both in vivo and in vitro, and has been proposed to be the metabolite responsible for ALDH2 inhibition by disulfiram. Diethyldithiocarbamate methyl ester (DDTC-Me), a key intermediate in the metabolism of disulfiram, has been shown to be bioactivated by microsomal monooxygenases to diethyldithiocarbamate methyl ester sulfoxide (DDTC-Me sulfoxide). Studies were conducted to determine if DDTC-Me sulfoxide was also an active metabolite of disulfiram and inhibitor of ALDH2. DDTC-Me sulfoxide inhibited ALDH2 in vitro with an IC50 of 10 microM, and in vivo with an ID50 of 31 mg/kg (170 mumol/kg). Maximal ALDH2 inhibition in vivo was observed 8 hr after the administration of 45.2 mg/kg DDTC-Me sulfoxide, with ALDH2 activity returning to control levels after 48 hr. Although DDTC-Me sulfoxide inhibited ALDH2 in vivo, DDTC-Me sulfoxide was not detected in plasma from rats treated with either disulfiram (75 mg/kg), DDTC-Me (122.25 mg/kg), or DDTC-Me sulfoxide (45.2 mg/kg). However, DDTC-Me and S-methyl N,N-diethylthiolcarbamate (DETC-Me) were detected in plasma from rats treated with DDTC-Me sulfoxide. In rats treated with DDTC-Me sulfoxide and challenged with ethanol, a small increase of approximately microM in blood acetaldhyde and an inconsistent drop in blood pressure was observed. In conclusion, DDTC-Me sulfoxide inhibited ALDH2 in vitro and in vivo, was less potent than DETC- MeSO, and was not detected after disulfiram administration.

S-methyl N,N-diethylthiolcarbamate sulfone, an in vitro and in vivo inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase

S-Methyl N,N-diethylthiolcarbamate sulfone (DETC-Me sulfone) was investigated for its rat liver mitochondrial low Km aldehyde dehydrogenase (ALDH2) inhibitory properties. DETC-Me sulfone inhibited ALDH2 in vitro (IC50 = 3.8 microM) and in vivo (ID50 = 170 mumol/kg; 31 mg/kg). Maximum inhibition (60%) of ALDH2 was observed 8 hr after DETC-Me sulfone administration. In addition, incubation of S-methyl N,N-diethylthiolcarbamate (DETC-Me) or S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-Me sulfoxide) with rat liver microsomes and an NADPH-generating system failed to produce DETC-Me sulfone. Furthermore, DETC-Me sulfone could not be detected in plasma from rats treated with either DETC-Me sulfoxide or DETC-Me sulfone. In conclusion, DETC-Me sulfone inhibited ALDH2 in vitro and in vivo. However, there was no evidence suggesting that DETC-Me sulfoxide was metabolized to DETC-Me sulfone.

In vivo pharmacodynamic studies of the disulfiram metabolite S-methyl N,N-diethylthiolcarbamate sulfoxide: inhibition of liver aldehyde dehydrogenase

S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) is proposed to be the metabolite of disulfiram responsible for the in vivo inhibition of liver low Km aldehyde dehydrogenase (ALDH) in the rat. Studies were conducted in male Sprague-Dawley rats and also in vitro using both rat liver mitochondrial and purified bovine mitochondrial low Km ALDH to investigate further the pharmacodynamic and pharmacokinetic characteristics of DETC-MeSO. Administration of DETC-MeSO to rats produced a rapid and maximal inhibition of liver mitochondrial low Km ALDH within 2 hr, which was still inhibited 30% after 168 hr. After DETC-MeSO treatment, the maximum plasma concentration of DETC-MeSO was reached within 0.5 hr, with DETC-MeSO being undetectable 2 hr after DETC-MeSO dosing. Although a trace amount of DETC-Me was detected in the plasma 0.5 hr after DETC-MeSO administration to rats, this disappeared within 1 hr. When rats were treated with disulfiram, the maximal plasma concentration of DETC-MeSO was found within 2 hr, with only a very small quantity of DETC-MeSO still detectable after 8 hr. Rats also were given the disulfiram metabolites diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), and S-methyl N,N-diethylthiolcarbamate (DETC-Me), and plasma analyzed for DETC-MeSO 2 hr after the administration of these metabolites. DETC-MeSO was detected in plasma, further illustrating that DETC-MeSO can be found in plasma after the administration of either disulfiram, or the subsequent in vivo metabolites DDTC, DDTC-Me, or DETC-Me.(ABSTRACT TRUNCATED AT 250 WORDS)

NADPH-dependent, regioselective S-oxidation of a thionosulfur- and thioether-containing xenobiotic, diethyldithiocarbamate methyl ester by rat liver microsomes

The present study describes the NADPH-dependent, regioselective oxidation of diethyldithiocarbamate methyl ester (DDTC-Me), a dithiocarbamate ester containing both a thionosulfur (C = S) and a thioether (S-CH3) group, to two novel S-oxidized metabolites. DDTC-Me is a key metabolite in the overall bioactivation pathway for the clinically used alcohol deterrent, disulfiram. Incubation of DDTC-Me with rat liver microsomes resulted in the formation of two major metabolites. These metabolites were identified as DDTC-Me sulfoxide [S(O)CH3] and DDTC-Me sulfine (C = S+-O-) based on their NMR spectra and by MS. The formation of DDTC-Me sulfoxide was completely inhibited by the cytochrome P-450 inhibitors, emulgen 911 and 1-benzylimidazole, but only partially inhibited by heat inactivation of the flavin-containing moonooxygenases (FMO). This suggested that DDTC-Me sulfoxide formation is primarily catalyzed by cytochrome P-450 with a minor contribution from FMO. In contrast, the formation of DDTC-Me sulfine was inhibited from 60 to 80% in the presence of emulgen 911 and 1-benzylimidazole and 30 to 50% by heat inactivation of FMO, suggesting a partial role of FMO in the formation of DDTC-Me sulfine. DDTC-Me sulfoxide is a new class of dithiocarbamates that has not been previously described, whereas, DDTC-Me sulfine belongs to a class of thionosulfur sulfines that have been implicated in a number of toxicological processes.

Role of flavin-dependent monooxygenases and cytochrome P450 enzymes in the sulfoxidation of S-methyl N,N-diethylthiolcarbamate

Disulfiram is bioactivated to S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO), the metabolite proposed to be responsible for the action of disulfiram as an aldehyde dehydrogenase inhibitor. This bioactivation process includes a reduction, an S-methylation, and two successive oxidations. Sulfur-containing functional groups are substrates for cytochrome P450 enzymes or flavin-containing monooxygenases (FMO). In the present study, we investigated the contribution of these monooxygenases to the formation of DETC-MeSO from its immediate precursor S-methyl N,N-diethylthiolcarbamate (DETC-Me). Liver microsomes obtained from mature male rats were incubated with DETC-Me. The formation of DETC-MeSO was blocked completely by solubilization of the microsomes with the detergent Emulgen 911, or by the presence of the cytochrome P450 inhibitor 1-benzylimidazole. However, thermal-inactivation of FMO resulted in only a partial loss in DETC-MeSO formation. Liver microsomes from phenobarbital-treated rats showed a 4- to 5-fold increase in the rate of formation of DETC-MeSO, compared with controls. Liver microsomes from pyrazole-treated rats showed a 50% decrease in the sulfoxidation of DETC-Me compared with controls. In a purified reconstituted system, cytochrome P450 2B1 (CYP2B1) catalyzed the formation of DETC-MeSO at a rate of 51 nmol DETC-MeSO formed/min/nmol cytochrome P450. Antibodies to CYP2B1 caused a 60% inhibition of DETC-MeSO formation by liver microsomes from phenobarbital-treated rats. These results suggest that in male rat liver microsomes, cytochrome P450 plays a major role in catalyzing the sulfoxidation of DETC-Me, whereas FMO plays a minor role (< 10%). Also, in liver microsomes from phenobarbital-treated rats, CYP2B1 is the major catalyst for the sulfoxidation of DETC-Me.

Bioactivation of S-methyl N,N-diethylthiolcarbamate to S-methyl N,N-diethylthiolcarbamate sulfoxide. Implications for the role of cytochrome P450

Diethyldithiocarbamate (DDTC), diethyldithiocarbamate methyl ester (DDTC-Me), S-methyl N,N-diethylthiolcarbamate (DETC-Me) and S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) are all metabolites of disulfiram. All inhibit rat liver low Km aldehyde dehydrogenase (ALDH) in vivo, with the order of potency being DETC-MeSO > DETC-Me > DDTC-Me > DDTC. Studies were carried out both in vivo and in vitro to further investigate the role of bioactivation as a requirement for the action of disulfiram as a liver ALDH inhibitor. The cytochrome P450 inhibitor 1-benzylimidazole (NBI) was employed as a pharmacological tool to study the metabolism of DETC-Me to DETC-MeSO. Administration of NBI to rats prior to DETC-Me treatment blocked the inhibition of liver mitochondrial low Km ALDH by DETC-Me. This was accompanied by an increase in plasma DETC-ME and a decrease in plasma DETC-MeSO. Pretreatment of rats with NBI prior to DETC-MeSO administration did not block the inhibition of liver mitochondrial low Km ALDH by DETC-MeSO. In in vitro studies, the inclusion of NBI in an incubation containing rat liver microsomes, mitochondria and an NADPH-generating system blocked the formation of DETC-MeSO and inhibition of liver mitochondrial low Km ALDH by DETC-Me. DETC-MeSO was found to be a potent inhibitor of rat liver mitochondrial low Km ALDH both in vivo and in vitro. The data suggest that the metabolism of DETC-Me to DETC-MeSO is mediated by cytochrome P450, and that inhibition of cytochrome P450 by inhibitors such as NBI block the inhibition of low Km ALDH by DETC-Me.

In vitro and in vivo inhibition of rat liver aldehyde dehydrogenase by S-methyl N,N-diethylthiolcarbamate sulfoxide, a new metabolite of disulfiram

In summary, these data provide the first evidence that DETC-MeSO is a natural metabolite of disulfiram, and a potent inhibitor of rat liver mitochondrial low Km ALDH both in vitro and in vivo. It is therefore proposed that, based upon evidence to date, DETC-MeSO appears to be the chemical species to which disulfiram must be bioactivated, and is the metabolite most likely responsible for disulfiram's inhibition of rat liver mitochondrial low Km ALDH in vivo. Characterization of the properties of DETC-MeSO as the metabolite responsible for disulfiram's action as an ALDH inhibitor is presently in the process of being completed.

Disulfiram metabolism as a requirement for the inhibition of rat liver mitochondrial low Km aldehyde dehydrogenase

In humans and animals, disulfiram produces a disulfiram-ethanol reaction after an ethanol challenge, the basis of which is the inhibition of liver aldehyde dehydrogenase (ALDH). Disulfiram and the metabolites diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), and S-methyl-N,N-diethylthiolcarbamate (DETC-Me) were studied in order to determine the role of bioactivation in disulfiram's action as an inhibitor of rat liver mitochondrial low Km ALDH (RLM low Km ALDH). In in vitro studies, disulfiram and DDTC (0.01 to 2.0 mM) both inhibited RLM low Km ALDH in a concentration-dependent manner. The addition of rat liver microsomes to the mitochondrial incubation did not further increase disulfiram-induced RLM low Km ALDH inhibition. However, DDTC-induced RLM low Km ALDH inhibition was increased further, but only at DDTC concentrations less than 0.05 mM. DDTC-Me and DETC-Me (2.0 mM) similarly exhibited an increased RLM low Km ALDH inhibition after the addition of liver microsomes. In in vivo studies, disulfiram (75 mg/kg), DDTC (114 mg/kg), DDTC-Me (41.2 mg/kg) or DETC-Me (18.6 mg/kg) administered i.p. to female rats inhibited RLM low Km ALDH. Inhibition of drug metabolism by pretreatment of rats with the cytochrome P450 inhibitor N-octylimidazole (NOI) (20 mg/kg, i.p.) prior to either disulfiram, DDTC, DDTC-Me or DETC-Me administration blocked the inhibition of RLM low Km ALDH. The in vitro and in vivo data support the conclusion that bioactivation of disulfiram to a reactive chemical species is required for RLM low Km ALDH inhibition and a disulfiram-ethanol reaction.

S-methyl-N,N-diethylthiolcarbamate: a disulfiram metabolite and potent rat liver mitochondrial low Km aldehyde dehydrogenase inhibitor

S-methyl-N,N-diethylthiolcarbamate-methyl ester (DETC-Me), a proposed disulfiram metabolite, was investigated both in vivo and in vitro for its effectiveness as a liver mitochondrial low Km aldehyde dehydrogenase (L Km ALDH) inhibitor. Male Sprague-Dawley rats were treated intraperitoneally with DETC-Me, killed at various times and L Km ALDH determined. DETC-Me was found to be a more potent in vivo inhibitor of L Km ALDH than either disulfiram, diethyldithiocarbamate (DDTC) or diethyldithiocarbamate-methyl ester (DDTC-Me). The ID50 for DETC-Me, DDTC-Me and disulfiram was 6.5, 15.5 and 56.2 mg/kg, respectively. The ID50 for DDTC was similar to DDTC-Me. Maximal inhibition of L Km ALDH occurred 30 minutes after DETC-Me administration. DETC-Me was ineffective as an in vitro inhibitor. DETC-Me produced a marked disulfiram-ethanol reaction (DER) at one-quarter of the dose of disulfiram or DDTC. Plasma DETC-Me in rats was greater after DETC-Me administration than after DDTC-Me, DDTC or disulfiram. In conclusion, DETC-Me is proposed to be a metabolite of disulfiram, and may be the immediate precursor of the chemical species responsible for L Km ALDH inhibition.

Comparative aspects of disulfiram and its metabolites in the disulfiram-ethanol reaction in the rat

Diethyldithiocarbamate-methyl ester (DDTC-Me), a metabolite of disulfiram, has been shown recently to produce a disulfiram-ethanol reaction (DER). Studies were carried out to compare the ethanol-sensitizing properties of DDTC-Me with those of disulfiram and diethyldithiocarbamate (DDTC) in the rat. All three drugs inhibited liver mitochondrial low Km aldehyde dehydrogenase (ALDH) in vivo, with maximal ALDH inhibition occurring 8 hr after drug administration. The onset of ALDH inhibition was most rapid after DDTC-Me administration. ALDH was inhibited approximately 50% 0.5 hr after DDTC-Me, whereas ALDH was inhibited only 5 and 10%, respectively, after disulfiram and DDTC. Not until 8 hr after drug treatment was ALDH inhibition the same for disulfiram, DDTC and DDTC-Me. The degree of ALDH inhibition from 8 to 172 hr after dosing was the same for all three drugs. An ethanol (1 g/kg, 20% v/v) challenge administered to rats treated with disulfiram (75 mg/kg), DDTC (114 mg/kg), or DDTC-Me (41.2 mg/kg) for 8 hr produced similar blood acetaldehyde/ethanol concentration-time profiles. In addition, all three agents produced a DER (hypotension, tachycardia). No DER occurred if ethanol was administered more than 24 hr after drug pretreatment. The hypotension associated with the DER correlated with the increased blood acetaldehyde but not blood ethanol. A threshold blood acetaldehyde of 110 microM appeared to be required for hypotension to occur, and this was related to ALDH inhibition of approximately 40%. The tachycardia associated with the DER correlated more with blood ethanol. After DDTC-Me administration, no disulfiram or DDTC could be detected in the plasma. Furthermore, no DDTC-Me was found in the plasma 8 hr after DDTC-Me administration, suggesting that no correlation exists between the DER and plasma concentration of DDTC-Me and most likely disulfiram. These data suggest that the alcohol-sensitizing properties of DDTC-Me are similar to those observed with disulfiram and DDTC. Since DDTC-Me is an active metabolite and more potent than disulfiram and DDTC in producing a DER, disulfiram metabolism is an important consideration in the disulfiram-ethanol reaction.

Diethyldithiocarbamic acid-methyl ester: a metabolite of disulfiram and its alcohol sensitizing properties in the disulfiram-ethanol reaction

Diethyldithiocarbamic-acid-methyl ester (DDTC-Me) is a major metabolite of disulfiram. When given to rats, DDTC-Me was found to inhibit the liver mitochondrial low Km aldehyde dehydrogenase (ALDH) without having any effect on the high Km isoenzyme. Inhibition of low Km ALDH by DDTC-Me in vivo exhibited a dose-response relationship, with inhibition of ALDH from 11% to 90% found when DDTC-Me was administered in a dose range from 1.8 to 158 mg/kg, IP. After a single dose of DDTC-Me (41.2 mg/kg, IP), the low Km ALDH was inhibited for 168 hours suggesting an irreversible enzyme inhibition. After an ethanol challenge to DDTC-Me-treated rats, a decrease in mean arterial pressure (MAP) and increase in heart rate was observed. Decreases in MAP occurred almost immediately after ethanol challenge and remained low throughout a four hour post-ethanol period. These results suggest that in vivo administration of DDTC-Me can cause an alcohol-sensitizing reaction, and that DDTC-Me actually may be the metabolite of disulfiram which produces the disulfiram-ethanol reaction. It is proposed the reaction be more correctly identified as the DDTC-Me-Ethanol Reaction or D-MER.

Isolated perfused lung histamine release, lipid peroxidation, and tissue superoxide dismutase from rats exposed to normobaric hyperoxia

Female Sprague-Dawley inbred rats were exposed to either 1 atm of 100% O2 for 24 h, or 65% O2 for 5 days, with or without pretreatment with disulfiram, an inhibitor of lung CuZn-SOD. After O2 exposure, the rats were killed, the lungs removed, and isolated perfused lungs (IPLs) prepared. The IPLs were perfused with modified Krebs-Henseleit buffer, and perfusate histamine, malondialdehyde (MDA), and lung tissue CuZn-SOD activity examined. Disulfiram administration decreased the LT50 of O2-exposed rats from 65 to 36 h. Histamine and MDA in the perfusate from the IPL prepared from rats exposed to 100% O2 for 24 h were markedly increased. When rats were pretreated with disulfiram and exposed to 100% O2 for 24 h, histamine and MDA were increased an additional 77% and 45%, respectively. In separate experiments, 100% O2 exposure significantly decreased lung CuZn-SOD activity by 40% while IPL histamine and MDA were significantly increased. However, exposure of rats to 65% O2 for 5 days decreased lung CuZn-SOD by 69% but did not affect IPL histamine release or perfusate MDA. These studies suggest that IPL histamine release and/or MDA may be an early biochemical marker for pulmonary O2 toxicity, that lung CuZn-SOD activity may not be the only determinant in O2 toxicity, and other defense mechanisms may play a vital protective role during sublethal O2 exposures.

Disulfiram-ethanol reaction in the rat. 1. Blood alcohol, acetaldehyde, and liver aldehyde dehydrogenase relationships

Studies were carried out to determine whether the disulfiram-ethanol reaction (DER) in the rat could be correlated with blood acetaldehyde, ethanol, and liver aldehyde dehydrogenase (ALDH) inhibition. Both hypothermia and hypotension were used as indices of the DER. Female Sprague-Dawley rats were given disulfiram (DSF) (100 mg/kg, i.p.) and low and high liver ALDH determined. No effect on high Km ALDH was found. Inhibition of low Km ALDH was dependent on DSF pretreatment time, with significant inhibition observed at 6, 8, and 12 hr following DSF. In rats receiving ethanol only, maximal blood ethanol was reached within 120 min. Blood acetaldehyde was almost undetectable. No change in rat core temperature was observed. In rats pretreated with DSF (100 mg/kg, i.p.) 8 hr before ethanol challenge (1 g/kg, i.p.), a marked increase in blood acetaldehyde was found and remained elevated throughout the temperature and blood pressure monitoring period. Blood ethanol reached a maximum within 90 min and then declined. Maximal hypothermia and hypotension occurred 120 min after ethanol. The administration of the dopamine receptor blocker pimozide (0.5 mg/kg, i.p.) 60 min before ethanol challenge, attenuated the hypothermia and hypotension. Pimozide was effective when given either 60 min before ethanol or 30 min after ethanol. The onset and duration of hypothermia and hypotension during the DER appears to follow the rise and fall of blood ethanol but not blood acetaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)

Elimination kinetics of disulfiram in alcoholics after single and repeated doses

Elimination kinetics of disulfiram were determined in 15 male alcoholics after 250 mg disulfiram taken by mouth as a single dose and again after 12 days of dosing. Apparent t 1/2s were calculated for disulfiram, diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), diethylamine (DEA), and carbon disulfide (CS2) and were found to be 7.3, 15.5, 22.1, 13.9, and 8.9 hr. Elimination t 1/2 for CS2 in breath was 13.3 hr. Average time to reach maximal plasma concentration after either single or repeated doses was 8 to 10 hr for disulfiram, DDTC, DDTC-Me, DEA, and CS2 in breath, while plasma CS2 concentration peaked 5 to 6 hr after disulfiram. In these studies, 22.4% and 31.3% of the disulfiram after single and repeated dosing was eliminated in the breath during one dosing interval. In urine, 1.7% and 8.3% of the disulfiram dose was eliminated as DDTC-glucuronide after single and repeated dosing, while DEA accounted for 1.6% and 5.7% of the dose. There was marked intersubject variability in plasma levels of disulfiram and its metabolites. This variability may be the result of the lipid solubility of disulfiram, differences in plasma protein binding, or the effect of enterohepatic cycling.

Hypothermia as an index of the disulfiram-ethanol reaction in the rat

Decreased core temperature in female rats was investigated as one possible index of the disulfiram-ethanol reaction (DER). Core temperature was decreased in rats in a dose-dependent manner when ethanol was administered to rats treated with disulfiram 8 hours before the ethanol challenge. The decrease in temperature began within 20 minutes after ethanol administration, reaching a maximal decrease between 60 and 120 minutes post ethanol. The core temperature returned to normal 300 minutes after ethanol. The blood pressure (carotid cannulation) decreased along with the core temperature. Maximal hypotension was found 120 minutes post ethanol, and returned to normal 300 minutes after ethanol. Heart rate increased initially and returned to normal 40 minutes after ethanol challenge.

The effect of in vivo hyperoxic exposure on the release of endogenous histamine from the rat isolated perfused lung

Female rats were exposed to either 1 atm air or 100% O2 for 12, 24, or 48 hr. The rats were killed, the lungs were removed, and an isolated perfused lung (IPL) system was prepared. The isolated lung preparation was perfused with a modified Krebs-Henseleit buffer in a recirculating system, and the effect of the O2 exposures on histamine release from the IPL was determined. The effect of these O2 exposures on malondialdehyde formation in the IPL also was examined. Maximal release of histamine occurred after 20 min of perfusion. A linear relationship was found between the maximal histamine concentration released into the perfusate and the length of time the rats were exposed to normobaric hyperoxia. Malondialdehyde in lung perfusate also increased in a linear manner with increasing O2 exposure time. Addition of the H1-receptor antagonist, d-chlorpheniramine, to the perfusate completely inhibited basal histamine release from the IPL of both air- and O2-exposed rats, while addition of the H2-receptor antagonist, metamide, potentiated the release process. There was no significant effect demonstrated when an equimolar concentration of atropine was added to the perfusate. Arterial plasma histamine from rats exposed to 100% O2 for 24 hr increased 40% when compared to air-exposed controls, while histamine release from the IPL increased 75%. In conclusion, exposure of rats to normobaric hyperoxia caused both histamine release and malondialdehyde formation. Histamine release probably occurred as a result of a free radical-induced peroxidation of the lipid membrane of histamine-containing mast cells. Release of histamine from the IPL may be an early biochemical marker of damage by O2.

Case report of acute disulfiram overdose

The authors describe the clinical symptoms of a disulfiram overdose in a male patient and present the plasma concentrations of disulfiram and its metabolites 4 and 7 days after the overdose.

Diethyldithiocarbamic acid-methyl ester distribution, elimination, and LD50 in the rat after intraperitoneal administration

Following the intraperitoneal administration of S35 diethyldithiocarbamic acid-methyl ester (S35 DDTC-Me) to male rats, maximal total radioactivity (S35) in most tissues was found 1 hr after dosing. Twelve hr after intraperitoneal S35 DDTC-Me, most of the total radioactivity was found in urine. The feces accounted for approximately 15% of the total radioactivity. No radioactivity was detected in the breath. The kidney exhibited the greatest uptake of radioactivity, while the least uptake was found in the brain and heart. Most of the radioactivity in the tissues was due to the inorganic sulfate. S35 DDTC-glucuronide was found in the gastrointestinal tract and feces. The LD50 for DDTC-Me given intraperitoneally to male rats and mice was 167 and 263 mg/kg, respectively. Symptoms of toxicity preceding death of the animals resembled those symptoms observed with disulfiram toxicity.

Elimination characteristics of disulfiram over time in five alcoholic volunteers: a preliminary study

The authors studied the elimination of disulfiram and its metabolites for 24 hours after disulfiram administration in five healthy male alcoholic volunteers. Using high-performance liquid chromatography, they found that a single 500-mg dose resulted in a gradual increase in plasma disulfiram and its metabolites, with peak levels generally occurring 8 hours after dosing. There was considerable interpatient variability (e.g., in one volunteer no disulfiram was detected during the entire 24-hour sampling period). The authors also found that breath carbon disulfide was 9.1% of the dose of disulfiram administered, which is less than that expected theoretically.

NAD+ and NADH in brain cortex from mice exposed to high oxygen pressure

Experiments were done in vivo to determine the effect of oxygen at high pressure (OHP) on NAD+ and NADH in mouse brain cortex. A 7% decrease (N.S.) in NADH was found in brain cortex from mice exposed to 6 atm of 100% oxygen for 8 min, while a 20% decrease (P less than 0.01) in cortical NADH, when compared to controls, occurred when mice were exposed to this oxygen pressure for either 16 min or 48 min. A 20% decrease (P less than 0.05) in cortical NADH was also observed in mice which had been killed during hyperactivity (a state preceding convulsions), at seizure onset, or 10 s post-convulsions. No measurable change in cortical NAD+ was observed at any of these oxygen exposure times or stages of toxicity. When mice were exposed to either 3.5 atm or 6 atm of oxygen for 16 min, a statistically significant decrease in cortical NADH (P less than 0.01) coupled with an increase in the NAD+/NADH ratio was found only at 3.5 atm and 6 atm, and not at 1 atm. The decrease in cortical NADH and increase in the NAD+/NADH ratio were reversed when mice were decompressed and exposed to air for 30 min. Disulfiram, a drug found to delay the onset of oxygen seizures, did not prevent the oxygen-induced decrease in cerebral NADH or increase in the NAD+/NADH ratio. The decrease in cortical NADH in mice exposed to OHP did not correlate with the onset of oxygen-induced convulsions.

Glutathione and non-protein sulfhydryl in cerebral cortex and lung in mice exposed to high oxygen pressure

Mice were exposed to 6 atm of 100% O2, and killed at the onset of hyperactivity, convulsions, and 10(s) post convulsions. Examination of brain cortex from mice killed at these stages of O2 toxicity revealed no change in oxidized glutathione (GSSG), non-protein sulfhydryls (NPSH), total glutathione (GSH + GSSG), the GSH/GSSG ratio, glutathione reductase and glutathione peroxidase. Mice exposed to 4 atm for 1 h or 6 atm for 16 min exhibited a 36% and 33% decrease in lung NPSH respectively, but no change in cortical NPSH was observed. Although intraventricular diethylmaleate (DEM) decreased cerebral NPSH 72%, no change in the susceptibility of mice to O2 convulsions was found. Disulfiram, an effective O2 convulsive protectant had no effect on either cortical NPSH or total glutathione.

Disulfiram distribution and elimination in the rat after oral and intraperitoneal administration

35S disulfiram (DSF), 7 mg/kg, was administered as a single dose to rats both orally (p.o.) or intraperitoneally (i.p.). The 35S DSF was rapidly absorbed by either route. Kidney, pancreas, liver, and the gastrointestinal tract exhibited the greatest uptake of radioactivity, while the least was found in brain. Preferential tissue uptake was similar with both routes of administration. Seven percent of the dose was excreted in the feces. Approximately 12% of the dose was eliminated by the breath as CS2. The 35S-DSF was rapidly metabolized to the 35S-diethyldithiocarbamate-glucuronide and 35S inorganic sulfate. Approximately 93% of the radioactivity was accounted for 48 hr after p.o. or i.p. 35S administration.

Determination of disulfiram and metabolites from biological fluids by high-performance liquid chromatography

A high-performance liquid chromatographic method is described for the determination of disulfiram, diethyldithiocarbamate, diethyldithiocarbamate methyl ester, carbon disulfide, and diethylamine from a single sample of plasma or urine. The analytical procedure is based on a quantitative stepwise extraction of disulfiram and diethyldithiocarbamate methyl ester, or the conversion of diethyldithiocarbamic acid, carbon disulfide and diethylamine to diethyldithiocarbamate methyl ester for chromatographical determination. The procedure is specific, precise and simple. The application of the analytical methods developed for the determination of disulfiram and the various metabolites in plasma from mice given disulfiram intraperitoneally or humans given Antabuse orally is illustrated.

Radioactive and nonradioactive methods for the in vivo determination of disulfiram, diethyldithiocarbamate, and diethyldithiocarbamate-methyl ester

Although disulfiram (tetraethylthiuram disulfide; DSF) has been used in the treatment of alcoholism for almost a quarter of a century, little is known about its in vivo metabolism. One reason for this is that few analytical methods are available that can determine DSF and its various metabolites in biologic fluids and tissues. This article describes two simple procedures for the determination of these substances.

Cerebral oxidized and reduced nicotinamide-adenine dinucleotide phosphate and glucose 6-phosphate dehydrogenase in mice during exposure to high oxygen pressure

NADP+, NADPH and glucose 6-phosphate dehydrogenase were determined in the cerebral cortex of mice exposed to high O2 pressure for 0, 8 and 16 min. These time intervals corresponded to 0, 50 and 100% of the CT50 (the time taken for 50% of the mice to convulse). Cerebral NADP+, NADPH and glucose 6-phosphate dehydrogenase also were determined in O2-exposed mice exhibiting hyperactivity, convulsions, and in mice killed 10s after convulsions. Similar increases in cortical NADP+ and decreases in NADPH were found in mice exposed to 610kPa (6 atm.) of 100% O2 for 0, 50 and 100% of the CT50, during hyperactivity, onset of seizure and 10s after convulsions. The NADP+/NADPH ratio increased approx. 25% at 0% of the CT50, and remained at this increased value at all O2-exposure periods including the hyperactive state, onset of seizure and 10s after convulsions. Identical changes in cerebral NADP+ , NADPH and the NADP+/NADPH ratio were found in mice exposed for 16min to 100% O2 at 100, 350 or 610kPa. No change in cerebral glucose 6-phosphate dehydrogenase was found in mice exposed to 610kPa of 100% O2 during the various stages of O2 toxicity. Only in the 10s post-convulsive group was a statistically significant decrease in glucose 6-phosphate dehydrogenase observed. Disulfiram [bis(diethylthiocarbamoyl) disulphide], an effective O2-protective agent, did not prevent the O2-induced increase in cerebral NADP+ and the NADP+/NADPH ratio, or decrease in NADPH.

A rapid and simple radioactive method for the determination of disulfiram and its metabolites from a single sample of biological fluid or tissue

An analytical method is described for the determination of radioactive disulfiram, diethyldithiocarbamate, diethyldithiocarbamate-methyl ester, diethyldithiocarbamate-glucuronide, inorganic sulfate, and a protein bound S35 fraction from a single sample of either plasma, urine or tissue. The procedure is based upon quantitative stepwise extraction or precipitation of the individual compounds, and is both specific and precise. The applicability of the methods developed for the determination of S35 disulfiram and its S35 metabolites in plasma and urine from a dog given S35 disulfiram i.v., and in mouse brain from mice given S35 disulfiram i.p. are illustrated.