Lipid peroxidation and protein thiol depletion are not involved in the cytotoxicity of N-hydroxy-2-acetylaminofluorene in isolated rat hepatocytes

Freshly isolated rat hepatocytes were used to study the mechanism of cell death induced by N-hydroxy-2-acetylaminofluorene (N-OH-AAF). Exposure to 1.0 mM N-OH-AAF resulted in more than 90% cell death (as measured by LDH leakage) of hepatocytes isolated from male rats within 6 hr. Only 36% of the hepatocytes isolated from female rats died within this period. When inorganic sulfate was omitted from the incubation medium, a 6 hr exposure to 1.0 mM N-OH-AAF resulted in only 40% cell death of male hepatocytes. These findings are in accordance with the sex difference and sulfation dependence of N-OH-AAF hepatotoxicity observed in the rat in vivo. N-OH-AAF decreased glutathione (GSH) in male hepatocytes in a concentration-dependent manner. This GSH consumption was only partly dependent on the presence of inorganic sulfate. No lipid peroxidation was observed during N-OH-AAF exposure; N-OH-AAF even prevented endogenous and diethyl maleate (DEM)-induced lipid peroxidation. No reduction of free protein thiol groups was found after exposure to N-OH-AAF, even after 75% cell death had occurred. A reduction of protein thiols after N-OH-AAF exposure was observed in GSH depleted hepatocytes (obtained by DEM plus vitamin E pretreatment). Under these conditions N-OH-AAF-induced cell death occurred earlier. Therefore, GSH protects against protein thiol depletion by N-OH-AAF in control cells. N-OH-AAF-induced cell death was preceded by a loss of intracellular ATP. It is concluded, therefore, that neither lipid peroxidation nor depletion of protein thiols, but possibly loss of intracellular ATP, is involved in the sulfation-dependent cytotoxic mechanism of N-OH-AAF in isolated rat hepatocytes.     

New leupeptin analogues: synthesis and inhibition data

Syntheses of several tripeptide analogues of leupeptin containing C-terminal argininal, lysinal, or ornithinal units are presented. The synthetic analogues were tested as inhibitors of trypsin, plasmin, and kallikrein. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) was significantly less effective as an inhibitor of trypsin and plasmin activity than leupeptin. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) and (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) display different inhibition characteristics than (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a). While (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) showed moderate inhibition of all three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) was less effective as an inhibitor of trypsin and plasmin activity. Of the three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) showed significant inhibition of kallikrein activity only. Modifications made in the composition and sequence of the P2 and P3 amino acids also resulted in variations in the inhibitory activity of the analogues. In general, plasmin showed a strong preference for inhibitors which contain an L-phenylalanyl-L-leucyl or an L-leucyl-L-valyl unit in the P2 and P3 positions.     

Binding profile of SM-9018, a novel antipsychotic candidate

The present study employed various receptor-binding assays to clarify the biochemical characteristics of SM-9018. SM-9018 possessed very high affinity for 5-HT2, D2 and 5-HT1A receptors (Ki = 0.61, 1.4 and 2.9 nM, respectively), and it had moderate affinity for alpha 1 and D1 receptors (Ki = 17 and 41 nM, respectively). However, SM-9018 had only negligible affinity for alpha 2, opiate, glutamate, phencyclidine, benzodiazepine and GABAA receptors. These results suggest that SM-9018 may be a novel antipsychotic agent with binding affinity for 5-HT2 and 5-HT1A receptors.     

Behavioral, biochemical and neurotoxicological actions of the alpha-ethyl homologue of p-chloroamphetamine

The present set of experiments was designed to examine the effects of extension of the alpha-methyl of p-chloroamphetamine (PCA) to an alpha-ethyl. Therefore, the alpha-ethyl homologue of PCA, 1-(4-chlorophenyl)-2-aminobutane (CAB), was compared to PCA in a number of pharmacological assays. CAB was 2-fold less potent than PCA at inhibiting synaptosomal uptake of [3H]5-hydroxytryptamine ([3H]5-HT), and 5-fold less potent at inhibiting uptake of [3H]dopamine ([3H]DA). In drug discrimination assays, CAB was approximately 3-fold less potent than PCA in animals trained to discriminate 3,4-methylenedioxymethamphetamine (MDMA) or its alpha-ethyl homologue, S-(+)-N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (S-(+)-MBDB), from saline. Monitoring with in vivo microdialysis, 10 mg/kg of PCA caused a large increase in extracellular DA and a significant decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. In contrast, 11 mg/kg CAB caused no increase and 22 mg/kg CAB caused only a slight increase in extracellular DA. Both doses of CAB caused a decrease in extracellular DOPAC. The potential 5-HT neurotoxicity of CAB was examined by measuring monoamine and metabolite levels and [3H]paroxetine binding at one week following acute doses. A 10 mg/kg dose of PCA caused an 80% decrease in cortical and hippocampal serotonergic markers, while an equimolar dose of CAB decreased only hippocampal 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels. However, 22 mg/kg of CAB produced a 20-40% decrease in all serotonergic markers. Thus, extension of the alpha-alkyl significantly decreases the dopaminergic effects of PCA. The similar decrease in relative 5-HT neurotoxicity and the decreased ability to alter dopaminergic systems in vivo and in vitro supports the involvement of DA in the neurotoxicity of PCA.     

Recycling suitability of wash waters from mosquito abatement vehicles and equipment into spray diluent

In response to changing laws as well as increased concern over environmental pollution, there is a current need to examine the best means of disposal of wash water generated by mosquito abatement operations. A study of wash waters from 6 central California mosquito abatement districts shows that herbicide levels were low enough so as not to preclude the use of these waters for recycling back into insecticide spray diluent. In one case, oil levels were high and an oil/water separation is probably necessary to prevent gum formation and clogging of spray equipment. Recycling of wash waters appears to be a feasible solution to the disposal problem once water contaminant levels are defined.     

Infantile glaucoma in Down's syndrome (trisomy 21)

We examined five patients with Down's syndrome and bilateral infantile glaucoma. In the first few months of life four patients had large cloudy corneas, breaks in Descemet's membrane, increased intraocular pressure, photophobia, and tearing. In one patient the diagnosis was delayed until 3 1/2 years of age because of concomitant nasolacrimal duct obstruction. Two patients developed cataracts and retinal detachment and have undergone multiple surgical procedures. The clinical course in these two older patients suggests that coexistence of congenital glaucoma, severe myopia, and cataracts in patients with trisomy 21 strongly predisposes for the development of retinal detachment and poor visual outcome.