Cytogenetic studies on commercial hexane solvent.

Commercial hexane is a solvent mixture of six-carbon isomers, consisting principally of n-hexane, 3-methylpentane, methylcyclopentane and 2-methylpentane. The potential of commercial hexane to produce chromosome aberrations was evaluated in both an in vitro assay using Chinese hamster ovary (CHO) cells and an in vivo cytogenetics assay using Sprague-Dawley rats. The CHO cells were exposed to media containing commercial hexane at concentrations of 0.014-0.42 microliters ml-1 in the presence and absence of an S-9 activation mixture. Cellular toxicity was observed at the higher dose levels, but no increase in chromosome aberrations was observed in either the non-activated or S-9-activated systems. For the in vivo cytogenetics assay, rats were exposed nose-only for 6 h per day for 5 consecutive days to commercial hexane vapor at target concentrations of 900, 3000 and 9000 ppm. Bone marrow cells were collected at 6 and 24 h after the midpoint of the last exposure. Metaphase cells were examined microscopically for chromosome aberrations. No statistically significant increases in aberrant cells were observed in the commercial hexane-exposed animals of any dose group at either of the bone marrow harvest times. In conclusion, commercial hexane did not produce chromosomal mutations under the conditions of these studies.

Conjugation of benzo[a]pyrene metabolites by freshwater green alga Selenastrum capricornutum.

Benzo[a]pyrene (BaP) undergoes metabolic transformation in mammals via oxidative, hydrolytic, and conjugative processes; however, little is known concerning BaP conjugation in freshwater algae. It has been shown in this laboratory that BaP is metabolized by Selenastrum capricornutum via a dioxygenase pathway. This study describes the conjugation of BaP metabolites by a green alga, Selenastrum capricornutum. Cultures were exposed to 1160 micrograms/l [14C]BaP for 4 days at 23 degrees C under gold fluorescent lights on a diurnal cycle of 16 h light, 8 h dark. Of the total metabolites in the algal culture, 89% were present in media. BaP and non-conjugated metabolites were separated from conjugated metabolites by chromatography on neutral alumina columns using solvents of increasing polarity. Seventy-one percent of the BaP metabolites were conjugates of which 12.2%, 12.0% and 12.4% were sulfate ester and alpha- and beta-glucose conjugates, respectively. Conjugates that coeluted with sulfate esters were hydrolyzed with arylsulfatase, alpha- or beta-glucosidase; high performance liquid chromatography (HPLC) analysis indicated that the major product of each enzymatic hydrolysis was the 4,5-dihydrodiol (87.2, 69 and 53%, respectively). Eighty-six percent of the conjugates were acid labile following incubation for 2 h in 4 N HCl at 37 degrees C. To our knowledge this is the first demonstration of the metabolism of a polynuclear aromatic hydrocarbon by a freshwater green alga through a dioxygenase pathway and subsequent conjugation and excretion.

The half-lives of alkylating intermediates from diethylnitrosamine and N-nitrosopyrrolidine: a method for the measurement of metabolically generated reactive species.

The half-times of the alpha-hydroxylated intermediates formed during metabolism of diethylnitrosamine and N-nitrosopyrrolidine have been determined. The method for determining half-times involved in vitro enzymatic conversion of the nitrosamine to a hydroxylated intermediate followed by trapping of the alkylating species generated from the chemical decomposition of the intermediate as it flowed through a column containing bound nucleophile. Half-times of less than 1 min at pH 7.4, 37 degrees C, were calculated from the distribution of alkylation on the column and the known flow rate of metabolic intermediates through the column. The half-times may be short enough to significantly limit organ distribution.

A method for measuring the lifetime of chemically and metabolically generated electrophilic species.

A method is presented for the characterization of the reaction order and rate constant for chemically and metabolically generated reactive electrophilic intermediates. The procedure employs flow kinetics and trapping of the electrophilic species. Reactive agents or metabolic intermediates are passed through a column containing a bound nucleophilic reagent. The electrophilic species reacts at a characteristic rate while moving through the column at a fixed pH, temperature and rate of flow. The alkylation products formed during this reaction are quantified in individual column segments which correspond to time intervals. This provides data for the calculation of the lifetime of the short-lived species. The method may be used for agents having half-lives of 1 s to 30 min. Metabolic intermediates need not be isolated. Data is presented for the reaction rates of 1-methyl-1-nitrosourea (MNU), 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) and iodomethane. A metabolic activation system is described for the conversion of acetoxy-methylmethylnitrosamine (DMN-OAc) to hydroxymethylmethylnitrosamine (DMN-OH) and measurement of the stability of that intermediate. Hydroxymethylmethylnitrosamine was found to have a half-life of 28s at pH 7.4, 37 degrees C.

Synthesis of substituted 2-aminopyrrole analogs of lidocaine II.

The synthesis and local anesthetic and antiarrhythmic properties of eight substituted 2-diethylaminoacetamido-3-carbamyl-4-methylpyrroles are described. Three compounds showed significant local anesthetic activity by the guinea pig wheal test, and four showed antiarrhythmic activity against chloroform-induced ventricular arrhythmias in mice.

Synthesis of substituted 2-aminopyrrole analogs of lidocaine I.

The synthesis, local anesthetic, and antiarrhythmic properties of nine 2-diethylaminoacetamido-3-cyano-4-methyl-5-substituted pyrroles are described. All compounds showed local anesthetic activity by the guinea pig wheal test and antiarrhythmic activity for chloroform-induced ventricular arrhythmias in mice.

Selected cardiovascular and central properties of three lidocaine analogs.

Three analogs of lidocaine (benzyl carbamyl, benzyl nitrile and methyl nitrile) were synthesized and examined for cardiovascular and central activity. The benzyl carbamyl analog was more potent than lidocaine in lowering blood pressure but possessed only slight local anesthetic, antiarrhythmic and CNS-depressant activity. At 40 mg/kg the benzyl nitrile derivative was superior to lidocaine in protecting against chloroform-induced arrhythmias. The methyl nitrile analog was less active than the benzyl nitrile analog in most parameters examined. The benzyl nitrile derivative and lidocaine had similar potencies on blood pressure depression, local anesthetic activity and ability to protect against calcium chloride-induced arrhythmias. Unlike the benzyl carbamyl derivative both lidocaine and the benzyl nitrile compounds appear to depress the cardiovascular system via a common mechanism.