Reactive astrocytes induced by 2-chloroethanol modulate microglia polarization through IL-1β, TNF-α, and iNOS upregulation

The synthetic organic chemical, 1,2-dichloroethane (1,2-DCE), can cause brain edemas under subacute poisoning. Our previous studies indicated that neuroinflammation could be induced due to astrocytes and microglia activation during brain edemas in 1,2-DCE-intoxicated mice. However, the crosstalk between these two glial cells in 1,2-DCE-induced neuroinflammation remained unclear. In this study, primary cultured rat astrocytes and microglia, as well as an immortalized microglia cell line were employed to study the effects of 2-chloroethanol (2-CE, a 1,2-DCE intermediate metabolite in vivo) treated astrocytes on microglia polarization. Our current results revealed that 2-CE treated rat astrocytes were activated through p38 mitogen-activated protein kinase (p38 MAPK)/nuclear factor-κB (NF-κB), and activator protein-1 (AP-1) signaling pathways. Theses pathways were triggered by reactive oxygen species (ROS) produced during 2-CE metabolism. Also, astrocytes were more sensitive to 2-CE effects than microglia. Interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) expressions were upregulated in 2-CE-induced reactive astrocytes, enhancing IL-1β, TNF-α, and nitric oxide (NO) excretions, which stimulated microglia polarization. Therefore, the neuroinflammation induced by 1,2-DCE in mice's brains is probably triggered by reactive astrocytes.

2,2,2-Trichloroethanol lengthens the circadian period of Bmal1-driven circadian bioluminescence rhythms in U2OS cells

2,2,2-Trichloroethanol (TCOH) is responsible for the pharmacological actions of chloral hydrate (CH), and is a major metabolite of trichloroethylene. Human exposure to TCOH is known to be increasing. Recently, it was reported that TCOH causes a significant phase delay of Per2 expression in mouse liver when injected daily over the course of several days. However, it is not clear whether TCOH directly modulates the molecular clock. In the present study we used a cell-based assay system to test this possibility. We found that the daily oscillation period of Bmal1 was lengthened to 3 h following treatment with 1.5 mM TCOH, and increased to 5 h with 3 mM TCOH treatment. However, low concentrations of TCOH had no noticeable effects. The effect of TCOH on Per2 oscillation was marginal. Interestingly, serum from rats anesthetized with CH also modulated Bmal1 period, suggesting that exposure to anesthesia should be taken into consideration for circadian rhythm studies. In summary, our study reveals a direct regulation of TCOH on molecular clock.

Mutations of L293 in transmembrane two of the mouse 5-hydroxytryptamine3A receptor alter gating and alcohol modulatory actions

1 The goal of this study was to determine whether mutations of L293 at the 15' position of TM2 in the 5-HT(3A) receptor alter macroscopic current kinetics, and if these changes could account for alterations in alcohol modulation. Receptor function was assessed in Xenopus oocytes under voltage-clamp and in HEK293 cells with whole-cell patch-clamp recording and rapid drug application. 2 Examination of responses of L293C and L293S receptors to agonist alone revealed enhanced activation, deactivation, and desensitization rates relative to the wild-type receptor. The L293G mutation produced marked slowing of deactivation and desensitization rates. Increased potency of 5-HT and increased efficacy of the partial agonist, DA, was also observed in these mutant receptors. 3 Ethanol and trichloroethanol (TCEt) enhancement of receptor function was reduced or eliminated in receptors containing L293 mutations to C, G, or S. The L293I mutant receptor retained ethanol and TCEt sensitivity. Ethanol and TCEt enhanced activation rate in the wild-type, but not the L293G and L293S receptors. No relationship was observed between any physicochemical property of the substituted amino acids and the change in alcohol potentiation of function. 4 The changes in receptor-channel properties in the mutant receptors support the idea that the L293 residue has important roles in channel gating. Our findings indicate that loss of allosteric modulation by alcohols is not related in any simple way to changes in channel kinetic properties brought about by L293 mutants. We did not observe any evidence that L293 is part of an alcohol binding site.

The effects of long chain-length n-alcohols on the firing frequency of dopaminergic neurons of the ventral tegmental area

The dopaminergic neurons of the ventral tegmental area (DA VTA neurons) have been implicated in the reinforcing properties of drugs of abuse, including ethanol (ethyl alcohol). Ethanol increases the spontaneous firing frequency of DA VTA neurons in vitro, in both brain slices and acutely dissociated neurons, and also in vivo. In many systems, longer n-alkyl alcohols have a more potent effect than ethanol, and the potency is a function of the number of carbons in the alkyl chain. We studied n-alcohols of chain length 1 (methanol) to 5 (pentanol) on the firing rate of DA VTA neurons in brain slice preparations. All of the alcohols studied produced increases in the spontaneous firing frequency in DA VTA neurons; as the chain length increased, lower concentrations of the alcohols were needed to produce the same percentage increase in firing. With very high concentrations of all the alcohols except methanol, we observed apparent depolarization block of firing. In addition, trichloroethanol (TCE), the active metabolite of chloral hydrate, increased the firing frequency of DA VTA neurons, and the EC(40) (concentration to produce a 40% increase in firing rate) of TCE was below that of ethanol. These studies indicate that excitation of VTA dopamine neurons by n-alcohols is related to the chain length of the carbons. This is likely to be a characteristic of the ethanol-sensitive element of DA VTA neurons and may be useful in identifying the element of the membrane that is responsible for ethanol-induced excitation.

Phases of dormancy in Yam tubers (Dioscorea rotundata)

BACKGROUND AND AIMS

The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied.

METHODS

Plants of 'TDr 131' derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7 degrees N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30 d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 degrees C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12 d after treatment.

KEY RESULTS AND CONCLUSIONS

Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220 d in 'TDr 131'), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (<70 d in total), are influenced by PGRs and environmental conditions, and are therefore endo-/eco-dormant phases. To manipulate dormancy to allow off-season planting and more than one generation per year requires that the duration of Phase I is shortened.

Co-expression of the 5-HT(3B) subunit with the 5-HT(3A) receptor reduces alcohol sensitivity

Allosteric modulation of mouse 5-Hydroxytryptamine(3A) (5-HT(3A)) and 5-HT(3A/B) receptor function by ethanol and trichloroethanol (TCEt) was assessed in HEK293 cells with whole cell patch-clamp electrophysiological recordings. Ethanol enhanced 5-HT(3A) receptor function, but had no effect on mouse 5-HT(3A/B) receptor mediated currents. The enhancing action of trichloroethanol (TCEt) on mouse 5-HT(3A/B) receptor function was much less than that observed in the mouse 5-HT(3A) receptor. Where alcohol-induced increases in peak amplitude were observed, the slope of the 20-80% rising phase of current onset was also enhanced, suggesting that increases in activation rate may be one mechanism through which alcohols enhance function of the 5-HT(3) receptors.

Macrokinetic analysis of blockade of NMDA-gated currents by substituted alcohols, alkanes and ethers

Volatile hydrocarbon based CNS depressants including short chain alcohols and anesthetics act, in part, by inhibition of the excitatory effect of glutamate at the NMDA receptor. While effects of several of these volatile agents on NMDA-gated currents have been demonstrated, there has been no direct comparison of different chemical classes of CNS depressant drugs on NMDA-gated currents. Here, whole-cell voltage clamp measurements of currents gated by 100 microM NMDA from cultured cerebrocortical neurons were examined in the presence of varying concentrations of the alcohols ethanol and hexanol, the halogenated alcohol trichloroethanol, the halogenated alkane halothane and the halogenated ethers isoflurane and sevoflurane. All drugs tested showed concentration-dependent inhibition of NMDA-gated currents with anesthetic concentrations of each agent producing approximately 30% inhibition of the NMDA-gated current. A rapid-translation perfusion system was used to study the onset and offset kinetics of each of the volatile agents. Onset kinetics for the CNS depressants was similar with tau values near 100 ms. Offset kinetics was more variable with tau ranging from 88.2 ms for ethanol to 221.4 ms for trichloroethanol. These data indicate that a wide variety of volatile hydrocarbon based CNS depressants produce a similar inhibition of NMDA-gated currents and that the kinetics for these agents are inconsistent with an open channel block.

Trichloroethanol enhances the activity of recombinant human TREK-1 and TRAAK channels

Human TREK-1 and TRAAK (hTREK-1 and hTRAAK) are the recently cloned tandem pore-domain potassium channels that are highly expressed in the central nervous system (CNS). The roles of 2P domain K+ channels in general anesthesia and neuroprotection have been proposed recently. We have investigated the ability of 2,2,2-trichloroethanol (an active metabolite of the general anesthetic chloral hydrate (CH)) to modulate the activity of hTREK-1 and hTRAAK channels expressed heterologously in Chinese hamster ovary cells by using whole-cell patch-clamp recording. Trichloroethanol potentiated hTREK-1 and hTRAAK channel activity in a reversible, concentration-dependent manner. The parent compound CH also augmented the activity of both the channels reversibly. CH activation of hTREK-1 was transient followed by a rapid inhibition, whereas hTRAAK activation was not followed by inhibition. Deletions of the carboxy terminal domain (Delta89, Delta100 and Delta119) of hTREK-1 did not abolish sensitivity to TCE (20 mM) suggesting that C-terminal tail is not essential for the activation of hTREK-1 by TCE. The hTREK-1 currents consisted of an instantaneous and a time-dependent component. The time-dependent current was reduced by trichloroethanol (20 mM). Our findings identify TREK-1 and TRAAK channels as molecular targets for trichloroethanol and suggest that activation of these channels might contribute to the CNS depressant effects of CH.

Characterization of P2X3, P2Y1 and P2Y4 receptors in cultured HEK293-hP2X3 cells and their inhibition by ethanol and trichloroethanol

Membrane currents and changes in the intracellular Ca2+ concentration ([Ca2+]i) were measured in HEK293 cells transfected with the human P2X3 receptor (HEK293-hP2X3). RT-PCR and immunocytochemistry indicated the additional presence of endogenous P2Y1 and to some extent P2Y4 receptors. P2 receptor agonists induced inward currents in HEK293-hP2X3 cells with the rank order of potency alpha,beta-meATP approximately ATP > ADP-beta-S > UTP. A comparable rise in [Ca2+]i was observed after the slow superfusion of ATP, ADP-beta-S and UTP; alpha,beta-meATP was ineffective. These data, in conjunction with results obtained by using the P2 receptor antagonists TNP-ATP, PPADS and MRS2179 indicate that the current response to alpha,beta-meATP is due to P2X3 receptor activation, while the ATP-induced rise in [Ca2+]i is evoked by P2Y1 and P2Y4 receptor activation. TCE depressed the alpha,beta-meATP current in a manner compatible with a non-competitive antagonism. The ATP-induced increase of [Ca2+]i was much less sensitive to the inhibitory effect of TCE than the current response to alpha,beta-meATP. The present study indicates that in HEK293-hP2X3 cells, TCE, but not ethanol, potently inhibits ligand-gated P2X3 receptors and, in addition, moderately interferes with G protein-coupled P2Y1 and P2Y4 receptors. Such an effect may be relevant for the interruption of pain transmission in dorsal root ganglion neurons following ingestion of chloral hydrate or trichloroethylene.

Differential effects of anesthetics on mitochondrial K(ATP) channel activity and cardiomyocyte protection

BACKGROUND

Mitochondrial adenosine triphosphate-sensitive potassium (mitoK(ATP)) channels play a pivotal role in mediating cardiac preconditioning. The effects of intravenous anesthetics on this protective channel have not been investigated so far, but would be of importance with respect to experimental as well as clinical medicine.

METHODS

Live cell microscopy was used to visualize and measure autofluorescence of flavoproteins, a direct reporter of mitoK(ATP) channel activity, in response to the direct and highly selective mitoK(ATP) channel opener diazoxide, or to diazoxide following exposure to various anesthetics commonly used in experimental and clinical medicine. A cellular model of ischemia with subsequent hypoosmolar trypan blue staining served to substantiate the effects of the anesthetics on mitoK(ATP) channels with respect to myocyte viability.

RESULTS

Diazoxide-induced mitoK(ATP) channel opening was significantly inhibited by the anesthetics R-ketamine, and the barbiturates thiopental and pentobarbital. Conversely, urethane, 2,2,2-trichloroethanol (main metabolite of alpha-chloralose and chloral hydrate), and the opioid fentanyl potentiated the channel-opening effect of diazoxide, which was abrogated by coadministration of chelerythrine, a specific protein kinase C inhibitor. S-ketamine, propofol, xylazine, midazolam, and etomidate did not affect mitoK(ATP) channel activity. The significance of these modulatory effects of the anesthetics on mitoK(ATP) channel activity was substantiated in a cellular model of simulated ischemia, where diazoxide-induced cell protection was mitigated by R-ketamine and the barbiturates, while urethane, 2,2,2-trichloroethanol, and fentanyl potentiated myocyte protection.

CONCLUSIONS

These results suggest distinctive actions of individual anesthetics on mitoK(ATP) channels and provide evidence that the choice of background anesthesia may play a role in cardiac protection in both experimental and clinical medicine.

Multiple effects of trichloroethanol on calcium handling in rat submandibular acinar cells

The effect of trichloroethanol (TCEt), the active metabolite of chloral hydrate, on the intracellular concentration of calcium ([Ca(2+)](i)) was investigated in rat submandibular glands (RSMG) acini loaded with fura-2. TCEt (1 - 10 mM) increased the [Ca(2+)](i) independently of the presence of calcium in the extracellular medium. Dichloroethanol (DCEt) and monochloroethanol (MCEt) reproduced the stimulatory effect of TCEt but at much higher concentrations (about 6 fold higher for DCEt and 20 fold higher for MCEt). TCEt mobilized an intracellular pool of calcium, which was depleted by a pretreatment with thapsigargin, an inhibitor of the sarcoplasmic and endoplasmic reticulum calcium-dependent ATPases, but not with FCCP, an uncoupler of mitochondria. TCEt 10 mM inhibited by 50% the thapsigargin-sensitive microsomal Ca(2+)-ATPase. DCEt 10 mM and MCEt 10 mM inhibited the ATPase by 20 and 10%, respectively. TCEt inhibited the increase of the [Ca(2+)](i) and the production of inositol phosphates in response to carbachol, epinephrine and substance P. TCEt inhibited the uptake of calcium mediated by the store-operated calcium channel (SOCC). ATP and Bz-ATP increased the [Ca(2+)](i) in RSMG acini and this effect was blocked by extracellular magnesium, by Coomassie blue and by oxydized ATP (oATP). TCEt potentiated the increase of the [Ca(2+)](i) and of the uptake of extracellular calcium in response to ATP and Bz-ATP. TCEt had no effect on the uptake of barium and of ethidium bromide in response to purinergic agonists. These results suggest that TCEt, at sedative concentrations, exerts various effects on the calcium regulation: (1) it mobilizes a thapsigargin-sensitive intracellular pool of calcium in RSMG acini; (2) it inhibits the uptake of calcium via the SOCC; (3) it inhibits the activation by G protein-coupled receptors of a polyphosphoinositide-specific phospholipase C. It does not interfere with the activation of the ionotropic P2X receptors. The use of chloral hydrate should be avoided in studies exploring the in vivo responses to sialagogues.

Trichloroethanol alters action potentials in a subgroup of primary sensory neurones

We investigated the effects of 2,2,2-trichloroethanol (TCE), the active metabolite of chloral hydrate, on large-conductance calcium-activated K+ channels (BKCa channels) of dorsal root ganglion (DRG) neurones. In outside-out patches, 2 and 5 mM TCE increased the open probability of BKCa channels to 1.7-fold and 2.8-fold of control, respectively. In 50% of the cells investigated (group A) the action potential (AP) was shortened reversibly by TCE by 20% and the whole-cell outward-current was increased by 44%. Both effects could be antagonized by iberiotoxin. In a second group of neurone (group B), TCE prolonged the AP duration. The effects of TCE in group A, which was 20-fold more potent than ethanol on BKCa channels and AP might contribute to the described analgesic effect of chloral hydrate.

Trichloroethanol inhibits ATP-induced membrane currents in cultured HEK 293-hP2X3 cells

Membrane currents in response to the application of alpha, beta-methylene ATP (alpha,beta-meATP) were recorded by the whole-cell patch-clamp technique in human embryonic kidney 293 cells transfected with the human P2X3 receptor (HEK 293-hP2X3 cells). Trichloroethanol, the biologically active metabolite of chloral hydrate, but not ethanol itself concentration-dependently and reversibly inhibited the current responses. It was concluded that the reported analgesic effect of chloral hydrate may be due to the interruption of pain transmission in dorsal root ganglia expressing P2X3 receptors.

Inhibition by chloral hydrate and trichloroethanol of AMPA-induced Ca(2+) influx in rat cultured cortical neurones

The effects of chloral hydrate and its main metabolite 2,2, 2-trichloroethanol were investigated on the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-induced rise of intracellular Ca(2+) concentration ([Ca(2+)](i)) in cultured non-pyramidal cortical neurones of rats by using single-cell fura-2 microfluorimetry. AMPA elicited a concentration-dependent effect that peaked at 300 microM (EC(50), 7. 5 microM). Responses to AMPA (30 microM) were markedly inhibited by superfusion with chloral hydrate (IC(50), 4.5 mM) or trichloroethanol (IC(50), 0.9 mM). By contrast, ethanol (100 mM) caused only slight inhibition. In conclusion, the results demonstrate that chloral hydrate and especially its metabolite trichloroethanol, inhibit the AMPA-induced rise of [Ca(2+)](i) by depressing the entry of Ca(2) into cortical neurones via the AMPA receptor-channel.

Ethanol and trichloroethanol alter gating of 5-HT3 receptor-channels in NCB-20 neuroblastoma cells

Alcohol potentiation of 5-HT3 receptors was examined in NCB-20 neuroblastoma cells using whole-cell patch-clamp electrophysiological techniques. Activation of the receptor with the weak partial agonist dopamine (DA) was used to examine alcohol effects under conditions of full agonist occupancy, but low probability of channel opening. Dopamine activation of the receptor increased in a concentration-dependent manner (EC50=0.28 mM), and on average maximal responses to DA were 8.0+/-0.8% of the maximal response to 5-HT. Ethanol (EtOH) and trichloroethanol (TCEt) potentiated DA-activated ion current mediated by 5-HT3 receptors. Potentiation of responses to a maximally effective dopamine concentration averaged 52.0+/-8.0% for EtOH and 567+/-43% for TCEt, which was comparable to the potentiation observed when receptors were activated by a low concentration of 5-HT. The alcohols increased both the potency and efficacy with which dopamine activated the receptor. The observation that alcohols increase the maximal efficacy of dopamine activation of the receptor indicates that one action of alcohols on the 5-HT3 receptor is to increase the probability of channel opening independent of any effect on agonist affinity.

Haloalkane dehalogenases: steady-state kinetics and halide inhibition

The substrate specificities and product inhibition patterns of haloalkane dehalogenases from Xanthobacter autotrophicus GJ10 (XaDHL) and Rhodococcus rhodochrous (RrDHL) have been compared using a pH-indicator dye assay. In contrast to XaDHL, RrDHL is efficient toward secondary alkyl halides. Using steady-state kinetics, we have shown that halides are uncompetitive inhibitors of XaDHL with 1, 2-dichloroethane as the varied substrate at pH 8.2 (Cl-, Kii = 19 +/- 0.91; Br-, Kii = 2.5 +/- 0.19 mM; I-, Kii = 4.1 +/- 0.43 mM). Because they are uncompetitive with the substrate, halide ions do not bind to the free form of the enzyme; therefore, halide ions cannot be the last product released from the enzyme. The Kii for chloride was pH dependent and decreased more than 20-fold from 61 mM at pH 8.9 to 2.9 mM at pH 6.5. The pH dependence of 1/Kii showed simple titration behavior that fit to a pKa of approximately 7.5. The kcat was maximal at pH 8.2 and decreased at lower pH. A titration of kcat versus pH also fits to a pKa of approximately 7.5. Taken together, these data suggest that chloride binding and kcat are affected by the same ionizable group, likely the imidazole of a histidyl residue. In contrast, halides do not inhibit RrDHL. The Rhodococcus enzyme does not contain a tryptophan corresponding to W175 of XaDHL, which has been implicated in halide ion binding. The site-directed mutants W175F and W175Y of XaDHL were prepared and tested for halide ion inhibition. Halides do not inhibit either W175F or W175Y XaDHL.

Trichloroethanol impairs NMDA receptor function in rat mesencephalic and cortical neurones

The effects of 2,2,2-trichloroethanol, the active compound of the sedative-hypnotic chloral hydrate, were investigated on N-methyl-D-aspartate (NMDA)-induced increases in intracellular Ca2+ concentration ([Ca2+]i) in cultured mesencephalic and cortical neurones by means of the fura-2 method. Trichloroethanol inhibited the NMDA response in a concentration-dependent manner in cortical (IC50 = 2.76 mM) and mesencephalic neurones (IC50 = 1.12 mM), with a maximum effect of approximately 85 and 94%, respectively. Ethanol was considerably less potent than trichloroethanol. In conclusion, the trichloroethanol-induced impairment of NMDA receptor function may contribute to the sedative-hypnotic properties of chloral hydrate.

5-hydroxytryptamine3 (5-HT3) receptor-mediated depolarisation of the rat isolated vagus nerve: modulation by trichloroethanol and related alcohols

The ability of 2,2,2-trichloroethanol (TCE) and related alcohols to modify the 5-hydroxytryptamine3 (5-HT3) receptor-mediated depolarisation of the rat isolated cervical vagus nerve were investigated by extracellular electrophysiological recording using the 'grease gap' technique. TCE at millimolar concentrations increased the magnitude of the 5-HT3 receptor-mediated depolarisations of the rat vagus nerve by a number of agonists (5-HT, phenylbiguanide (PBG), quipazine). Concentration response curves generated for the 5-HT3 receptor agonists. 5-HT and PBG, in the absence and presence of TCE (5 mM) indicated that the potentiation in agonist-induced depolarisation was due to an increase in both agonist potency and apparent efficacy. Following apparent complete 5-HT3 receptor desensitisation (induced by either 5-HT or PBG; 100 microM for 90 min), application of TCE (5 mM) in the continued presence of either agonist induced a depolarisation of the vagus nerve. In addition to TCE, a number of related alcohols (tribromoethanol, isopentanol and 5-chloropentanol but not ethanol) at millimolar concentrations also potentiated depolarisation of the vagus nerve induced by 5-HT. Combined application of both TCE (0.1-20 mM) and isopentanol (20 mM) indicated that the potentiation of the 5-HT3 receptor-mediated depolarisation by these alcohols was not additive. The present studies indicate that the 5-HT3 receptor expressed on the cervical vagus nerve is susceptible to allosteric modulation by a number of alcohols including the anaesthetic agent TCE. Such an interaction may have relevance to the nausea and vomiting experienced by some patients following recovery from general anaesthesia.

Inhibition of excitatory amino acid-activated currents by trichloroethanol and trifluoroethanol in mouse hippocampal neurones

1. The effects of the active metabolite of chloral derivative sedative-hypnotic agents, 2,2,2-trichloroethanol (trichloroethanol), and its analog 2,2,2-trifluoroethanol (trifluoroethanol), were studied on ion current activated by the excitatory amino acids N-methyl-D-aspartate (NMDA) and kainate in mouse hippocampal neurones in culture using whole-cell patch-clamp recording. 2. Both trichloroethanol and trifluoroethanol inhibited excitatory amino acid-activated currents in a concentration-dependent manner. Trichloroethanol inhibited NMDA- and kainate-activated currents with IC50 values of 6.4 and 12 mM, respectively, while trifluoroethanol inhibited NMDA- and kainate-activated currents with IC50 values of 28 and 35 mM, respectively. 3. Both trichloroethanol and trifluoroethanol appeared to be able to inhibit excitatory amino acid-activated currents by 100 per cent. 4.Concentration-response analysis of NMDA- and kainate-activated current revealed that trichloroethanol decreased the maximal response to both agonists without significantly affecting their EC50 values. 5. Both trichloroethanol and trifluoroethanol inhibited excitatory amino acid-activated currents more potently than did ethanol. The inhibitory potency of trichloroethanol and trifluoroethanol appears to be associated with their increased hydrophobicity. 6. The observation that trichloroethanol inhibits excitatory amino acid-activated currents at anaesthetic concentrations suggests that inhibition of excitatory amino acid receptors may contribute to the CNS depressant effects of chloral derivative sedative-hypnotic agents.

Trichloroethanol modulation of recombinant GABAA, glycine and GABA rho 1 receptors

The actions of 2,2,2,-trichloroethanol were studied on agonist-activated Cl- currents in gamma-aminobutyric acid type A (GABAA), glycine and GABA rho 1 receptors by use of the whole-cell patch-clamp technique. Recombinant wild-type and mutant receptor subunits were transiently expressed in human embryonic kidney (HEK) 293 cells. Trichloroethanol enhanced currents elicited by submaximal (EC20) agonist concentrations at GABAA alpha 2 beta 1 receptors and glycine alpha 1 homomeric receptors in a reversible, concentration-dependent manner. Trichloroethanol, at concentrations of < or = 2 mM, did not significantly alter the magnitude of submaximal GABA currents at GABA rho 1 receptors, whereas higher concentrations inhibited submaximal GABA currents. Recent work has identified residues within putative transmembrane domains 2 and 3 as critical for positive modulation of GABAA and glycine receptors by n-alkanols and volatile ether anesthetics. Submaximal glycine currents at receptors containing either of two specific mutations within the glycine receptor alpha 1 subunit (S267I and A288W) were not enhanced by low concentrations of trichloroethanol and were inhibited by higher concentrations of trichloroethanol. In the GABAA alpha 2 beta 1 receptor, a specific mutation within transmembrane domain 3 of the beta 1 subunit (M286W) also abolished positive modulation by trichloroethanol. Mutations within the GABAA alpha 2 receptor subunit did not alter positive modulation by TCEt, whereas such mutations ablate positive modulation by n-alkanols and volatile anesthetics. In summary, trichloroethanol modulation of GABAA, glycine and GABA rho 1 receptors shares some, but not all, features in common with the requirements for modulation by n-alkanols and volatile anesthetics.

Alcohols potentiate the function of 5-HT3 receptor-channels on NCB-20 neuroblastoma cells by favouring and stabilizing the open channel state

1. 5-HT3 receptor-mediated ion current was recorded from NCB-20 neuroblastoma cells using the whole-cell patch-clamp technique. Rapid drug superfusion was used to study the mechanism of alcohol potentiation of 5-HT3 receptor function and to analyse effects of alcohols on receptor-channel kinetics in detail. 2. Trichloroethanol (TCEt) increased in a dose-dependent way the initial slope, 20-80% rise time and measured desensitization rate of the current induced by low concentrations (1-2 microM) of 5-HT. Ethanol (EtOH) and butanol (ButOH) had similar effects on the 5-HT3 receptor-induced current. 3. TCEt and ButOH decreased the measured desensitization rate of current induced by 10 microM 5-HT, a maximally effective concentration of agonist. These alcohols also increased the relative amplitude of steady state to peak current induced by 2 or 10 microM 5-HT, indicating a possible decrease in the intrinsic rate of desensitization. 4. TCEt also decreased the deactivation rate of the current activated by 2 microM 5-HT after a short pulse of agonist application. 5. Current sweeps generated by 1 microM 5-HT in the presence or absence of 10 mM TCEt or 100 mM EtOH were well fitted using a modified standard kinetic model derived from the nicotinic acetylcholine receptor. This analysis indicated that potentiation by alcohols could be accounted for by increases in the association rate constant coupled with decreases in the dissociation and desensitization rate constants. 6. This study suggests that alcohols potentiate 5-HT3 receptor-mediated current by both increasing the rate of channel activation and stabilizing the open state by decreasing the rates of channel deactivation and desensitization.

Alpha subunit isoform influences GABA(A) receptor modulation by propofol

We have investigated the role of the alpha subunit in the modulation of gamma-aminobutyric acid type A (GABA(A)) receptors by the general anesthetic propofol, using whole-cell patch clamp recordings made from distinct stable fibroblast cell lines which expressed only alpha1beta3gamma2 or alpha6beta3gamma2 GABA(A) receptors. At clinically relevant anesthetic concentrations, propofol potentiated submaximal GABA currents in alpha1beta3gamma2 receptors to a far greater degree than those in alpha6beta3gamma2 receptors. The alpha subunit influenced the efficacy of propofol for modulation, but not its potency. In contrast, direct gating of the ion channel by propofol, in the absence of GABA, was significantly larger in the alpha6 than the alpha1 containing receptors. The potentiation of submaximal GABA by trichloroethanol, and the potentiation and direct gating by methohexital was also studied, and showed the same relative trends as propofol.

Anti-serotonergic effects of urethane and chloral hydrate may not be mediated by a blockade of 5-HT2 receptors. Short communication

The general anesthetics urethane and chloral hydrate have profound anti-serotonergic effects both in the rat cortex in vivo and the rat aortic ring in vitro. The suggestion that these effects may be due to an action on 5-HT2 receptors was tested using ex vivo and in vitro [3H]ketanserin binding assays with membrane-enriched fractions from rat brain. Urethane did not alter [3H]ketanserin binding in the ex vivo assay. In the in vitro assay, urethane, chloral hydrate, and its active metabolite 2,2,2-trichloroethanol produced slight reductions (of 16%, 9%, and 18%, respectively) of [3H]ketanserin binding. These studies suggest that anti-serotonergic effects of urethane and chloral hydrate may not be mediated by a blockade of 5-HT2 receptors.

The interaction of trichloroethanol with murine recombinant 5-HT3 receptors

1. The effects of ethanol, chloral hydrate and trichloroethanol upon the 5-HT3 receptor have been investigated by use of electrophysiological techniques applied to recombinant 5-HT3 receptor subunits (5-HT3R-A or 5-HT3R-As) expressed in Xenopus laevis oocytes. Additionally, the influence of trichloroethanol upon the specific binding of [3H]-granisetron to membrane preparations of HEK 293 cells stably transfected with the murine 5-HT3R-As subunit and 5-HT3 receptors endogenous to NG 108-15 cell membranes was assessed. 2. Ethanol (30-300 mM), chloral hydrate (1-30 mM) and trichloroethanol (0.3-10 mM), produced a reversible, concentration-dependent, enhancement of 5-HT-mediated currents recorded from oocytes expressing either the 5-HT3R-A, or the 5-HT3R-As subunit. 3. Trichloroethanol (5 mM) produced a parallel leftward shift of the 5-HT concentration-response curve, reducing the EC50 for 5-HT from 1 +/- 0.04 microM (n = 4) to 0.5 +/- 0.01 microM (n = 4) for oocytes expressing the 5-HT3R-A. A similar shift, from 2.1 +/- 0.05 microM (n = 11) to 1.3 +/- 0.1 microM (n = 4), was observed in oocytes expressing the 5-HT3R-As subunit. Trichloroethanol (5 mM) had little or no effect upon the maximum current produced by 5-HT for either recombinant receptor. 4. Trichloroethanol (5 mM) similarly reduced the EC50 for 2-methyl-5-HT from 13 +/- 0.4 microM (n = 4) to 4.6 +/- 0.2 microM (n = 4) and from 15 +/- 2 microM (n = 4) to 5 +/- 0.4 microM (n = 4) for oocytes expressing the 5-HT3R-A and 5-HT3R-As subunit respectively. Additionally, trichloroethanol (5 mM) produced a clear enhancement of the maximal current to 2-methyl-5-HT (expressed as a percentage of the maximal current to 5-HT) from 63 +/- 0.7% (n = 4) to 101 +/- 1.6% (n = 4) and from 9 +/- 0.2% (n = 4) to 74 +/- 2% (n = 4) for oocytes expressing the 5-HT3R-A and 5-HT3R-As subunit respectively. 5. Trichloroethanol (2.5 mM) had no effect upon the Kd, or Bmax, of specific [3H]-granisetron binding to membrane homogenates of NG 108-15 cells or HEK 293 cells. Similarly, competition for [3H]-granisetron binding by the 5-HT3 receptor antagonists ondansetron and tropisetron was unaffected. However, competition for [3H]-granisetron binding by the 5-HT3 receptor agonists, 5-HT, 2-methyl-5-HT and phenylbiguanide was enhanced by trichloroethanol (2.5 mM). 6 Unexpectedly, the competition for [3H]-granisetron binding by the 5-HT3 receptor antagonist,quipazine, was enhanced by 2.5 mM trichloroethanol. Quipazine (1 nM-0.3 microM) antagonized 5-HT evoked currents recorded from oocytes expressing the 5-HT3R-A subunit with an IC50 of 18 +/- 3 nM(n = 4). Additionally, quipazine (30 nM-0.3 microM) produced a small inward current which was greatly enhanced by 5 mM trichloroethanol and antagonized by 100 nM ondansetron. Collectively, these observations suggest that quipazine may act as a partial agonist.7. The demonstration that a recombinant homo-oligomeric receptor, expressed in a foreign membrane,retains a sensitivity to alcohols, together with the sequencing of alcohol-insensitive 5-HT3 receptor subunits, may lead to a better definition of the alcohol binding site(s).

Relationship between glutathione concentration and metabolism of the pyrrolizidine alkaloid, monocrotaline, in the isolated, perfused liver

The influence of GSH concentration on metabolism of monocrotaline was examined in the isolated, perfused rat liver. Chloroethanol (0.37 mmol/kg), diethyl maleate (5.6 mmol/kg), and buthionine sulfoximine (72.9 mmol/kg) given in vivo reduced hepatic GSH from 3.7 mumol/g wet weight to 1.5, 0.6 and 0.9 mumol/g, respectively. Livers were then perfused in vitro for 1 hr with monocrotaline (0.5 mM). GSH depletion had no effect on the total release of pyrrolic metabolites of monocrotaline. Depletion, however, markedly affected the pattern of pyrrole release. Biliary release of 7-glutathionyl-6,7-dihydro-1-hydroxy-methyl-5H-pyrrolizine (GSDHP) was reduced by up to 72%. Pretreatment with diethyl maleate or buthionine sulfoximine increased the level of protein-bound pyrroles in the liver by 107 and 84%, respectively. Such pyrroles are probably responsible for liver toxicity. GSH depletion also led to a doubling of dehydromonocrotaline release into the perfusate. This metabolite is probably responsible for the extrahepatic toxicity of monocrotaline. Release into perfusate of the relatively nontoxic metabolite, 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) was correspondingly decreased. Hepatic GSH content was increased to 4.4 mumol/g by pretreatment with oxo-4-thiazolidine carboxylate (4.76 mmol/kg). This agent increased total pyrrolic metabolites by 54%. Biliary release of GSDHP and perfusate release of dehydromonocrotaline and DHP were all increased. Thus, hepatic GSH levels regulate the metabolism of monocrotaline and dehydromonocrotaline and, consequently, the hepatic and extrahepatic toxicity of monocrotaline. GSH depletion leads to a switch from the biliary release of the midly toxic GSDHP to the perfusate release of the highly toxic dehydromonocrotaline. GSH depletion also permits more dehydromonocrotaline in the liver to become available for macromolecular alkylation. These findings suggest that nutritional intake of sulfur-containing amino acids can influence the severity of pyrrolizidine poisoning.

Trichloroethanol potentiation of gamma-aminobutyric acid-activated chloride current in mouse hippocampal neurones

1. The action of 2,2,2-trichloroethanol on gamma-aminobutyric acid (GABA)-activated Cl- current was studied in mouse hippocampal neurones in tissue culture by use of whole-cell patch-clamp recording. 2. Trichloroethanol increased the amplitude of currents activated by 1 microM GABA or 0.1 microM muscimol. Trichloroethanol, 1-25 mM, potentiated current activated by 1 microM GABA in a concentration-dependent manner with an EC50 of 3.0 +/- 1.4 mM and a maximal response (Emax) of 576 +/- 72% of control. 3. Trichloroethanol potentiated currents activated by GABA concentrations < 10 microM, but did not increase the amplitude of currents activated by concentrations of GABA > or = 10 microM. Despite marked potentiation of currents activated by low concentrations of GABA, trichloroethanol did not significantly alter the EC50, slope, or Emax of the GABA concentration-response curve. 4. Trichloroethanol, 5 mM, potentiated GABA-activated current in neurones in which ethanol, 10-500 mM, did not. The effect of trichloroethanol was not altered by the putative ethanol antagonist, Ro 15-4513. Trichloroethanol did not potentiate currents activated by pentobarbitone. 5. In the absence of exogenous GABA, trichloroethanol at concentrations > or = 2.5 mM activated a current that appeared to be carried by Cl- as its reversal potential changed with changes in the Cl- gradient and as it was inhibited by the GABAA antagonists, bicuculline methiodide and picrotoxin. 6. Since trichloroethanol is thought to be the active metabolite of chloral hydrate and other chloral derivative anaesthetics, potentiation of the GABA-activated current in central nervous system neurones by trichloroethanol may contribute to the sedative/hypnotic effects of these agents.

Trichloroethanol potentiation of 5-hydroxytryptamine3 receptor-mediated ion current in nodose ganglion neurons from the adult rat

Trichloroethanol (TCEt) potentiated ion current mediated by 5-hydroxytryptamine (5-HT)3 receptors in isolated adult rat nodose ganglion neurons. The magnitude of potentiation of peak current amplitude increased with increasing TCEt concentrations from 0.5 to 5 mM. The rate of decay of current also increased as a function of TCEt concentration. Steady-state current was unaffected by TCEt at concentrations up to 10 mM. A high concentration of TCEt (25 mM) potentiated peak current but inhibited steady-state current. Potentiation appeared to involve an increase in agonist potency as the magnitude of potentiation of peak current decreased with increasing agonist concentration. Agonist application before TCEt treatment decreased the magnitude of potentiation elicited by 5 mM TCEt. These observations indicate that the potentiating action of TCEt arises from an increase in the efficacy with which 5-HT activates current. TCEt appears to facilitate transitions from closed to open states more readily than transitions from desensitized to open states. These observations are consistent with the hypothesis that 5-HT3 receptor function may contribute to the behavioral pharmacology of alcohols and related sedative/hypnotic agents.

Trichloroethanol potentiates synaptic transmission mediated by gamma-aminobutyric acidA receptors in hippocampal neurons

We have examined the actions of trichloroethanol (TCEt), the active metabolite of the general anesthetic chloral hydrate, on responses mediated by gamma-aminobutyric acid (GABA)A receptors in response to application of exogenous GABA and activation of endogenous GABAergic transmission, by using hippocampal neurons in cell culture and in brain slices. In the presence of TCEt, Cl- current activated by exogenous GABA was both enhanced in amplitude and prolonged, leading to a net increase in total charge passing through GABAA receptor channels. Prolongation of GABA-activated current increased in magnitude in a concentration-dependent manner from 0.2 to 10 mM TCEt. Inhibitory postsynaptic currents produced at synapses between pairs of cultured GABAergic neurons or by activation of interneurons in hippocampal slices were also prolonged by TCEt, at concentrations from 0.5 to 10 mM. Application of TCEt at concentrations of 1 mM and above produced a small amplitude current which was directed outwardly at -40 mV in neurons in which methylsulfate or gluconate was the major intracellular anion and directed inwardly in neurons filled with Cl-. Our observations indicate that TCEt potentiates GABAergic transmission; presumably by potentiating the function of GABAA receptors in a manner similar to barbiturate or steroid anesthetics. This action is likely to contribute to the general anesthetic effect of TCEt which occurs after chloral hydrate administration.

Sedative/hypnotic effects of chloral hydrate in the neonate: trichloroethanol or parent drug?

Although the metabolism and pharmacokinetics of chloral hydrate (CH) have been reported, there have been no attempts to correlate CH or its metabolite, trichloroethanol (TCE) with the sedative or hypnotic effects. In order to determine whether plasma concentrations of CH or TCE reflect the sedative/hypnotic effects, a sedation/agitation scale was developed. Based on the results of the present study, the sedative/hypnotic effects of TCE cannot be ruled out completely. However, in the neonate, the parent drug CH seems to have a more important role than has been previously suggested from human research.

Effects of non-electrolyte molecules with anesthetic activity on the physical properties of DMPC multilamellar liposomes

The effects of 13 non-electrolytes with moderate anesthetic potency on the order of DMPC liposomes were examined. Changes in order were monitored by steady-state fluorescence polarization techniques using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPG). At 30 degrees C, all of the compounds tested decreased the DPH steady-state anisotropy (rs), with potencies highly correlated to their oil/water partition coefficients. However, only the most hydrophobic anesthetics decreased TMA-DPH RS. Some of the most hydrophilic compounds, including ethanol and urethane, actually increased TMA-DPH rs, suggestive of an increase in membrane order. The concept of selectivity was borrowed from partitioning theory and used to explain some effects on anesthetic potency of decreasing temperature to 18 degrees C. In the gel as opposed to the liquid crystalline phase, selectivity for decreasing membrane order (as monitored by DPH) markedly increased, suggesting that anesthetic partitioning and/or the site of anesthetic action was occurring in a more hydrophobic domain. The solute-independent difference (or capacity) between two membranes for perturbation was defined as membrane sensitivity. Sensitivity appeared to also decrease with decreasing temperature, despite the decrease in membrane partitioning. This effect is thought to result from the selective delivery of the anesthetic solute to the membrane interior and away from more hydrophilic domains where anesthetics may order membrane structure.

Effect of 2(3)-tert-butyl-4-hydroxyanisole (BHA) and 2-chloroethanol against pyrrole production and chronic toxicity of monocrotaline in chickens

Pyrrolizidine alkaloids are found in numerous plant species throughout the world. Poultry losses due to feed contamination with seeds of Crotalaria species are well documented. Monocrotaline is the major toxic pyrrolizidine alkaloid of Crotalaria species. Studies in laboratory animals and chickens have shown a protective effect of 2(3)-tert-butyl-4-hydroxyanisole (BHA) from monocrotaline in both acute and chronic toxicity. 2-Chloroethanol is thought to interfere with the detoxification mechanisms of the alkaloids. Chickens were administered monocrotaline after separate groups were pretreated with BHA and 2-chloroethanol. There was an apparent deleterious effect of monocrotaline in 2-chloroethanol-pretreated chickens, similar to that in non-pretreated birds, with respect to growth rates, morbidity, mortality, and hepatic histopathology. Monocrotaline pyrrole formation was measured in chickens pretreated with BHA and 2-chloroethanol by means of the Erlich reagent reaction spectrophotometric assay. There was a significant difference in pyrrole production between the treatment groups. The 2-chloroethanol plus monocrotaline (40 mg/kg), BHA (500 mg/kg) plus monocrotaline, monocrotaline, BHA (100 mg/kg) plus monocrotaline (20 mg/kg), and BHA (500 mg/kg) plus 2-chloroethanol and monocrotaline groups had decreasing amounts of pyrrole metabolite formation respectively.

The use of suicide substrates to select mutants of Escherichia coli lacking enzymes of alcohol fermentation

Mutants of Escherichia coli resistant to chloroethanol or to chloroacetaldehyde were selected. Such mutants were found to lack the fermentative coenzyme A (CoA) linked acetaldehyde dehydrogenase activity. Most also lacked the associated fermentative enzyme alcohol dehydrogenase. Both types of mutants, those lacking acetaldehyde dehydrogenase alone or lacking both enzymes, mapped close to the regulatory adhC gene at 27 min on the E. coli genetic map. The previously described acd mutants which lack acetaldehyde dehydrogenase and which map at 63 min were shown to be pleiotropic, affecting respiration and growth on a variety of substrates. It therefore seems likely that the structural genes for both the acetaldehyde and alcohol dehydrogenases lie in the adhCE operon. This interpretation was confirmed by the isolation of temperature sensitive chloracetaldehyde-resistant mutants, some of which produced thermolabile acetaldehyde dehydrogenase and alcohol dehydrogenase and were also found to map at the adh locus. Reversion analysis indicated that mutants lacking one or both enzymes carried single mutations. The gene order in the adh region was determined by three point crosses to be trp-zch::Tn10-adh-galU-bglY-tyrT-chlC.

Mutagenicity of trichloroethylene, trichloroethanol and chloral hydrate in Aspergillus nidulans

A trichloroethylene (TCE) sample, free of epoxides, has been assayed for its ability to induce gene mutations (methionine suppressors) and mitotic segregation in the mould Aspergillus nidulans. No increase in the spontaneous frequency of methionine suppressors was observed when conidia of a haploid strain were plated on selective medium and exposed to TCE vapours. A weak but statistically significant increase in methionine suppressors was detected, however, when conidia of cultures grown and conidiated in the presence of TCE vapours were plated onto selective media. Growing colonies of a heterozygous diploid strain were exposed to TCE vapours to investigate the induction of mitotic segregation. Scoring and phenotypic analysis of segregant sectors showed a significant increase in the frequency of haploids and 'non-disjunctional' diploids but not of cross-overs. Treatment of quiescent conidia in liquid medium was ineffective. Trichloroethanol and chloral hydrate, two main TCE metabolites in mammals, shared the ability to induce somatic segregation demonstrated by TCE vapours. On the grounds of these results the possible endogenous metabolic conversion of TCE into trichloroethanol and chloral hydrate is hypothesized.

Inhibition of delta-aminolevulinic acid dehydratase by trichloroethylene

Male Wistar rats (8 animals/group; 180-200 g) were exposed continuously to trichloroethylene (TRI) for 48 or 240 h or methylchloroform (1,1, 1-trichloroethane: MC for 48 h at 50, 400 and 800 ppm. The inhibition of delta-aminolevulinic acid dehydratase (ALA-D) was examined in liver, blood and bone marrow of naive and phenobarbital pretreated animals exposed to TRI. A clear cut dose-effect relationship between the exposure concentration or duration of exposure and the inhibition of ALA-D activity was seen for rats exposed to TRI. In addition to this finding, significant interaction between TRI exposure and phenobarbital treatment was observed in the inhibition of ALA-D in liver and blood. MC did not produce inhibition. Trichloroacetic acid and trichloroethanol failed to inhibit the ALA-D activity in vitro. It seems that a metabolite(s) of TRI other than the above 2 substances may play a role in the inhibition of ALA-D. The inhibition of ALA-D (38% or 48% of the control in liver or in blood, respectively) observed after the 240 h exposure at 400 ppm to TRI was accompanied by the significant elevation of delta-aminolevulinic acid synthase (186% of the control) in liver and the increase in excretion of delta-aminolevulinic acid in urine (142% of the control). This occurred without an apparent weight loss, liver injury or hematological changes.

[Levels of glutathione and anaerobic glycolysis in the kidney and liver of rats treated with chloroethanol]

Chloroethanol administration produces in rats a strong fall of glutathione levels in liver and kidney tissues. In liver, such a modification does not imply alterations in the levels of glucose, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-biphosphate, lactate and pyruvate and in the glycolytic activity. In kidney, the glycolytic activity does not result modified, while it appears a reduction in levels of glucose, glucose-6-phosphate, fructose-1,6-biphosphate and triose phosphates and a remarkable increase of pyruvate. The administration of chloroethanol produces a strong fall of glutathione in the soluble and nuclear fractions of liver and in the soluble and mitochondrial fractions of kidney.

The effect of thermal injury on drug metabolism in the rat

Because of previously reported hepatic abnormalities in burns, the activity of the hepatic drug metabolizing system was assessed in burned Sprague-Dawley rats. In 16% burned male rats, pentobarbital sleeping times were significantly prolonged from day 1 to day 24 postburn, and trichloroethanol sleeping times were significantly prolonged from day 1 to day 10 postburn. The activity of p-nitroanisole O-demethylase was significantly depressed in male rats at 5, 10, and 17 days post-16% burn. In female rats, this enzyme was more depressed at 10 days post-16% burn than in male rats. A direct relationship was found between per cent burn and impairment of enzyme activity. The depression of drug metabolizing enzymes was inducible by phenobarbital pretreatment. Pretreatment with the immunosuppressive drug azathioprine prevented the enzyme depression at 5 days postburn, a result which possibly implicates a postburn hyperimmune response as the mechanism for the depressed enzyme levels.

The effects of ethylene chlorohydrin on fatty acid synthesis

Male chicks weighing 700 to 900 g. received an acute or eight doses IG of 60 or 40 mg/kg ethylene chlorohydrin (ECH) respectively and were sacrificed eighteen hours after the last dose. Mitochondrial elongation of fatty acids was decreased significantly while fatty acid synthetase activity was not significantly affected by ECH treatment. Cytochrome c oxidase activity in fresh whole liver homogenate was significantly higher in chicks subjected to acute exposure with ECH when compared to the controls. Upon freezing and thawing of homogenates, cytochrome c oxidase activity increased significantly in the control group but was unchanged in the ECH group which suggests that the mitochondrial membrane integrity is compromised by the ECH treatment. Serum and liver triglyceride levels were significantly elevated in both the single and multiple ECH dose groups. Liver to body weight ratios were significantly higher in both treatment groups when compared to their controls. Histological examination of the liver of ECH-treated chicks showed cytoplasmic clearing of the cells but no vacuolization or centrilobular necrosis. Serum isocitrate dehydrogenase levels were significantly higher in the multiple treatment ECH group than in the control group.

Comparison of the mutagenic potency of 2-chloroethanol, 2-bromoethanol, 1,2-epoxybutane, epichlorohydrin and glycidaldehyde in Klebsiella pneumoniae, Drosophila melanogaster and L5178Y mouse lymphoma cells

A series of 2 haloethanols and 3 epoxides was investigated in 3 mutagenicity test systems, namely (1) the fluctuation test in Klebsiella pneumoniae, (2) the sex-linked recessive lethal test in Drosophila melanogaster, and (3) the HGPRT test with L5178Y mouse lymphoma cells. The order of mutagenic potency was, in Klebsiella: glycidaldehyde greater than 2-bromoethanol = epichlorohydrin greater than 1,2-epoxybutane greater than 2-chloroethanol; in Drosophila: glycidaldehyde = epichlorohydrin greater than 1,2-epoxybutane; in mouse lymphoma cells: epichlorohydrin greater than 1,2-epoxybutane. The haloethanols were non-mutagenic in Drosophila. 2-Chloroethanol and glycidaldehyde were negative in mouse lymphoma cells. The high mutagenic potency of epichlorohydrin as compared with 1,2-epoxybutane was consistent in all systems, and with published data.

Human skin reaction to ethylene oxide

Many materials now used in hospitals are sterilized with EO. EO gas retained in porous materials, which have not been properly aired, can produce skin irritation. The experiments reported here were designed to determine the level of EO and duration of skin contact required to produce adverse effects. The role of EO by-products in such reactions was also investigated. To obtain this information, patches retaining EO or its by-products, EC and EG, were applied to the backs of human volunteers. The patches were removed at intervals between 1 and 8 hr and the reactions were observed. The resulting skin reactions directly related to the total dose of EO received. Patch materials that rapidly lose EO, such as fabric or rubber, produced few reactions, even at EO levels as high as 5000 ppm. A patch material that loses EO more slowly, PVC film, produced reactions at EO levels above 1700 ppm. The patch materials that retained EO the longest, thick PVC blocks and petrolatum applied to Webril pads, produced the most reactions. When the EO level in those materials approximated 1000 ppm or higher, skin reactions usually appeared after 4 to 8 hr contact. The level of reactivity among the volunteers was quite consistent. One subject, however, who developed sensitivity to EO, showed a mild delayed reaction to approximately 100 ppm of EO in PVC. The characteristics of that sensitivity are discussed. Since little or no reactions developed to the patches containing EO by-products, EO itself can be assumed to be the toxic agent. The experiments support the conclusion that the lowest level of EO which produces skin irritation in nonsensitized subjects approximates 1000 ppm, when retained in slow-airing material against the skin for 4 hr or more.

'Lactate type' response of ruminal fermentation to chloral hydrate, chloroform and trichloroethanol

In ruminal fluid, taken from a cow 2 h after cereal feeding and supplemented with powdered grass, chloral hydrate diminished the rate of acetate, butyrate and propionate production. Instead, a considerable increase in lactate production was elicited by the drug. Chloroform and trichloroethanol had the same effect. Chloral hydrate and chloroform rendered the redox potential more negative which indicates inhibition of methane production. A concentration of chloral hydrate (2 mM), giving complete methane inhibition, reduced volatile fatty acid production by 30%. The findings are explained by assuming that chloral hydrate blocks methane production but in addition is inhibitory at a step below lactate in the reductive pathway to propionate and that the conditions chosen resulted in substrate saturation of one of the enzymes in the succinate pathway to propionate.

[Gamma-rays and ethylene oxide sterilization (author's transl)]

For many years there was doubt if gamma-irradiated PVC materials could be sterilized with ethylene oxide. It was feared that toxic concentrations of ethylene chlorohydrin (2-chlorethanol) might originate with this procedure. We investigated the various possibilities of ethylene chlorohydrin formation. Gamma-irradiated PVC tubes were resterilized with ethylene oxide and the 2-chlorethanol concentrations determined by gas chromatography. The 2-chlorethanol concentrations at the end of sterilization ranged from 240 to 436 ppm depending upon the composition of the tubes. After 4 d they ranged from < 5 to 280 ppm and after 21 d from < 5 to 218 ppm. For comparison were examined PVC tubes which were not gamma-irradiated but ethylene oxide sterilized only. We extracted < 5 to 23 ppm ethylene chlorohydrin from them. PVC tubes gas sterilized only and retaining 44 to 9300 ppm ethylene oxide were submerged in physiological NaCl solution for 2 h. The ethylene chlorohydrin concentrations formed by this procedure ranged from 43 to 75 ppm. After 4 d aeration before begin of extraction they decreased to < 5, 10 and 16 ppm. PVC tubes aerated for 5 or 7 d, containing at least 236 ppm ethylene chlorohydrin did not demonstrate any effect upon cultures of human fibroblasts. The toxic concentrations of 2-chlorethanol in our own animal- and cell culture experiments were 12 000 ppm or higher. Other investigators found no damaging effect on mouse fibroblasts by adding 20 000 ppm ethylene chlorohydrin. It appears to be sufficiently proven that gamma-irradiated PVC items may be resterilized with ethylene oxide and used in patients provided they they have been adequately aerated.

2-Halogeno-ethanols as an uncoupler of phosphorylation in rat liver mitochondria

2-Chloroethanol, 2-bromoethanol and 2,2,2-trifluoroethanol at a concentration of 0.79 vol.% stimulated state 4 respiration and released oligomycin inhibition of state 3 respiration. 2-Fluoroethanol and 1-propanol at the same concentration did not affect the respiration.

Active site structural change of alpha-chymotrypsin due to 2-halogeno-ethanols; comparison with ethanol, I-propanol, and urea

2-Halogeno-ethanols change the active site structure of alpha-chymotrypsin more rapidly and effectively than ethanol, 1-propanol and urea, probably before producing an extensive conformation change.

The influence of trichloroethylene and related drugs on the vestibular system

A previously described experimental model for studying the effect of industrial solvents on the vestibular system of rabbits has been applied to trichloroethylene. Estimation of trichloroethylene and its metabolites in blood and cerebrospinal fluid was performed by gas chromatography. Vestibular function was studied by recording nystagmus, induced by positional changes or accelerated rotation. At blood levels of trichloroethylene above 30 p.p.m. "positional nystagmus" develops. Two metabolites of trichloroethylene, chloral hydrate and trichloroethanol, which are known as central nervous system (CNS) depressants, did not induce this abnormal nystagmus. However, alpha-chloralose, a derivative of chloral hydrate, induced positional nystagmus and also a markedly exaggerated nystagmus developed during rotatory acceleration. It is suggested that solvents like trichloroethylene elicit vestibular disturbances by stimulation of central subcortical vestibulo-oculomotor connections. The stimulation may be caused by a blockage of inhibitory systems.

Effect of 2-chloroethanol on hepatic microsomal enzymes in the rat

The effect of 2-chloroethanol on the activities of hepatic microsomal enzymes in the rat has been studied. A significant reduction in activities of drug-metabolizing enzymes (aminopyrine N-demethylase, coumarin 3-hydroxylase) and a marked decrease of glucose 6-phosphatase were seen in both sexes given dose levels of 20 mg/kg sc daily for 7 days. Inosine diphosphatase activity remained unaltered. In male rats given 3 or 10 mg/kg, a trend in the inhibition of drug metabolism was found. A single dose of 50 mg/kg caused no apparent change in the activities of the enzymes measured.

Induction of gene mutations and gene conversions by vinyl chloride metabolites in yeast

Chloroethylene oxide and 2-chloroacetaldehyde, two metabolites of vinyl chloride, and 2-chloroethanol, a putative metabolic intermediate, were assayed for their genetic activity in the yeasts Schizosaccharomyces pombe and Saccharomyces cerevisiae. Chloroethylene oxide was found to be the most effective in inducing forward mutations in Sch. pombe and gene conversions in S. cerevisiae, increasing the mutation and conversion frequencies 340 and 50 times, respectively, over those of the controls. In either the presence or the absence of mouse liver microsomes, 2-chloroacetaldehyde showed only feeble genetic activity, and 2-chloroethanol was completely inactive in both yeast strains. In contrast to vinyl chloride, 2-chloroacetaldehyde did not induce forward mutations in Sch. pombe inthe host-mediated assay in mice. The results strongly support the hypothesis that chloroethylene oxide is one of the principal mutagenic agents formed from vinyl chloride in the presence of mouse liver enzymes.

Vinyl chloride mutagenicity via the metabolites chlorooxirane and chloroacetaldehyde monomer hydrate

Mutagenicity tester strains of Bacillus and Salmonella were used to assay vinyl chloride in nutrient broth at a practical concentration level. Also screened without exogenous activation were seven potential metabolites of vinyl chloride in their pure forms as well as the related epichlorohydrin. Chlorooxirane, chloroacetaldehyde, chloroacetaldehyde monomer hydrate, chloroacetaldehyde dimer hydrate, chloroacetaldehyde trimer, and epichlorohydrin produced significant mutagenic acitivity in Salmonella typhimurium strains sensitive to base-pair mutation. A recombination repair deficient strain of Bacillus subtilis was inhibited in growth by these compounds, whereas excision repair deficient and wild type strains of Bacillus subtilis were relatively unaffected. On the basis of these assays a working hypothesis for the vinyl chloride carcinogenesis mechanism is proposed which involves chlorooxirane and chloroacetaldehyde monomer hydrate as the ultimate carcinogenic metabolites of vinyl chloride.