Studies on 5,5-diphenylhydantoin irreversible binding to rat liver microsomal proteins.

5,5-Diphenylhydantoin irreversibly binds to rat liver microsomes and the process requires NADPH and O2. Proteins binding was significantly enhanced when experiments were carried out with liver microsomal preparations from beta-naphthoflavone and 3-methylcholanthrene pretreated animals whereas pretreatment with phenobarbital significantly reduced it. Carbon monoxide, beta-diethylaminoethyl-diphenylpropylacetate and glutathione inhibited drug covalent binding to microsomal proteins. In contrast, enhanced drug binding was observed when trichloropropene oxide and cyclohexene oxide, two epoxide hydrolase inhibitors, were added to the incubation mixture. 5,5-Diphenylhydantoin in vitro metabolism was quantitatively determined by gas liquid chromatography with selected ion monitoring. A good correlation seems to exist between drug covalent binding and the microsomal process of 5,5-diphenylhydantoin hydroxylation to 5-(4-hydroxyphenyl)-5-phenylhydantoin. The results presented support a previous hypothesis on the intermediacy of arene oxides in the biotransformation of this drug.

Mutagenicity of diphenylhydantoin and some of its metabolites towards salmonella typhimurium strains.

The mutagenicities of 5,5-diphenylhydantoin (DPH) and its major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) were tested in vitro using different Salmonella strains (TA1535, TA100, TA1537, TA1538, TA98). Experiments were carried out at various concentrations in the absence and in the presence of an activating system consisting of hepatic S9 fraction from control rats and from rats pretreated with phenobarbital (PB), beta-naphthoflavone (BNF), 3-methylcholanthrene (3-MC) and Aroclor 1254 (PCB). DPH slightly increased the number of revertants per plate only after incubations with TA1538 in the presence of the S9 fraction from the liver of 3-MC- and PCB-pretreated animals. A similar but more significant frameshift mutation was observed for HPPH on both TA98 and TA1538 strains and in conditions of metabolic activation by the liver microsomal fractions of rats after pretreatment with BNF, 3-MC and especially PCB. Parallel experiments on the metabolism of DPH to HPPH and of HPPH to the catechol derivative in vitro support the hypothesis of an involvement of epoxide intermediates in the mutagenic activity of DPH.

Isolation and partial characterization of temperature bacteriophages from enteropathogenic strains of Escherichia coli 0111:K58.

We report studies on ten strains of Escherichia coli 0111:K58 isolated from children with acute diarrhea. Our results show that these E. coli strains do not produce the pathogenic factors of enterotoxic E. coli (ETEC) and are lysogenic for phages belonging to two groups that differ for host range, kinetics of thermal inactivation, antigenicity and morphology. These data support the hypothesis that these phages may in vivo contribute to reduction of the number of common E. coli strains by lytic infection favouring the development of the enteropathogenic strain of E. coli.

Mutagenicity studies on tiopronin.

alpha-Mercaptopropionylglycine (tiopronin, Mucolysin), a drug endowed with an interesting mucolytic activity, was tested for mutagenicity by means of the following in vitro and in vivo tests: mutagenesis on S. typhimurium with and without metabolic activation, genetic mutation on S. pombe P1 with and without metabolic activation, gene conversion on S. cerevisiae D4 with and without metabolic activation, urinary assay in the mouse with S. cerevisiae D4, host mediated assay in the mouse with S. cerevisiae D4 and micronucleus test in the mouse. On the basis of the results obtained tiopronin proved to be free of mutagenic activity.