Disposition of polychlorinated dibenzo-p-dioxins, dibenzofurans, and non-ortho polychlorinated biphenyls in pregnant long evans rats and the transfer to offspring.

Pharmacokinetic properties of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDFs), and non-ortho biphenyls (PCBs) play a critical role in their relative toxicity. The present study examined the transfer of these chemicals to offspring and placenta. Pregnant Long Evans rats received 0.0 (control), 0.05, 0.2, 0.8, and 1.0 microg/kg of dioxin toxic equivalence (TEQ) by oral gavage on the 15th gestational day (GD 15), using a dosing mixture that contained 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,7,8-pentachlorodibenzofuran (1-PeCDF), 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF), octachlorodibenzofuran (OCDF), 3,3',4,4'-tetrachlorobiphenyl (PCB 77), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), and 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169) in ratios approximating that in food. Rats were euthanized on GD 16, GD 21, and postnatal day 4 (PND 4). The chemical concentrations in fetus, pup, placenta, and maternal liver, serum, and adipose tissue were determined using gas chromatography/high-resolution mass spectrometry. A dose-dependent increase in hepatic sequestration was seen with TCDD, PeCDD, 4-PeCDF, OCDF, PCB 126, and PCB 169, and the transfer to offspring was reduced at higher doses. 4-PeCDF, PeCDD and PCB 126 showed higher liver affinity than TCDD. TCDF, 1-PeCDF, and PCB 77 were metabolized rapidly. On GD 16, TCDD and the three PCBs reached equilibration between the fetus and placenta, but this did not occur with PeCDD and 4-PeCDF until GD 21, according to the lipid-based concentrations. Offspring compartments received more of the dosed compounds lactationally than transplacentally (7-28% versus 0.5-3%). The behavior of each congener was dose-dependent; therefore, extrapolation of high-dose experimental data should be used with caution.

Fragmentation of 3,7-dialkyl-1,5-diphenyl-3,7-diazabicyclo[3.3. 1]nonan-9-ones under electron ionization.

A series of 3,7-dialkyl-1,5-diphenyl-3,7-diazabicyclo[3.3. 1]nonan-9-ones was prepared, and the details of their fragmentation under electron ionization (EI) were elucidated. The molecular ions of each compound under consideration were quite abundant in their EI spectra. Full-scan spectra exhibited a number of fragment ions which were clearly assigned using MS/MS and accurate mass measurements. The basic fragmentation of 3,7-dialkyl-1,5-diphenylbispidinones was due to the cleavage of C(1)-C(2) bond followed by a hydrogen migration similar to an odd-electron McLafferty rearrangement. Alternatively, the C(1)-C(2) bond cleavage was followed by the elimination of an imine molecule, Alk-N=CH(2). Further fragmentation resulted in ions at m/z 234 and 103, present in the spectra of all the compounds under study. The fragmentation pathways proposed in this paper are based on the substituent shifts, accurate mass measurements and collision-induced dissociation spectra of selected ions. The results of the present work can be useful in selecting the fragment ions suitable for identification and quantitation of bispidinones in biological matrices.

Fast atom bombardment/tandem mass spectrometry of physalaemin-like peptides.

Fragment ion spectra obtained from collision-induced decomposition of protonated molecular ions have been used to determine amino acid sequences of several physalaemin-like peptides which were recently purified from rabbit stomach. This technique was chosen because the peptides were available in microgram quantities and were anticipated to contain pyroglutamate as the blocked N-terminal residue. Such spectra of several synthetic analogs of the naturally occurring peptides were obtained and analyzed to confirm the veracity of this peptide sequencing strategy. In addition, methyl ester derivatives of these synthetic peptides provided a crucial test for the spectral interpretation via the mass shifts thus induced.

Enhancement of structural information in FAB ionized carbohydrate samples by neutral gas collision.

Fast atom bombardment (FAB) ionization and two coupled analyzers (BE-EB) have been combined with neutral gas collision (C) to enhance structural information in the mass spectra of oligosaccharides. (B and E are abbreviations for magnetic and electric sectors respectively.) FAB ionization and the first analysers (BE) have provided parent ions free from biological and liquid matrix contaminants. Structural detail of these products were observed after collision and daughter ion analysis in a second coupled analyser (EB). Starting from complex mixtures, this instrumental approach, BE-C-EB, has provided specific oligomeric sequence information which was not observed in the normal FAB mass spectra. Collision spectra obtained from isomeric linear and branched oligosaccharides show unique fragments that can be directly related to structure.

Identification of the major metabolite of 4,4'-thio-bis-(6-t-butyl-m-cresol).

Metabolism of 4,4'-thio-bis-(2-t-butyl-5-methylphenol)(TBBC) in rats resulted in the formation of a glucuronide conjugate of TBBC. This conjugate was identified by a combination of high-performance liquid chromatography (HPLC) and mass spectrometry and a tandem mass spectrometric method employing a fast particle ionization technique. A comparison of mass spectral data from the in-vivo metabolite of TBBC and an enzymically synthesized glucuronide conjugate of TBBC showed the metabolite to be the monoglucuronide.

In vitro metabolism of [3H] corticosterone by mammary glands from lactating rats. Isolation and identification of 21-acyl[3H]corticosterone.

[3H] Corticosterone undergoes extensive 21-acylation on incubation with minced mammary glands from lactating rats. A purified 21-acyl [3H] corticosterone fraction was obtained by subjecting extracts of the incubated tissues to Sephadex LH-20 column chromatography followed by partitioning between n-heptane/methanol. The methanol extracts were chromatographed consecutively on columns of silica gel and C18-silanized (reverse-phase) silica gel. The radioactive product was methoximated and re-chromatographed on the reverse-phase column. Mass spectral analysis of the 21-acyl [3H] corticosterone 3,20-dimethoxime and synthetic corticosterone 21-oleate 3,20-dimethoxime suggested identity. Confirmation of the precise nature of the 21-acyl moiety was obtained by isotope dilution analysis of the underivatized radiometabolite with corticosterone 21-oleate. The composition of the 21-acyl [3H] corticosterone fraction (i.e. before extensive purification) was ascertained by isotope dilution analysis with various corticosterone esters. It appears that [3H] corticosterone 21-oleate is a major component of this fraction, representing 80% of the radioactivity; [3H] corticosterone 21-linoleate is a minor component, i.e. 8.6%. [3H] Corticosterone 21-palmitate, [3H] corticosterone 21-arachidonate, and [3H] corticosterone 21-stearate, if indeed present, constitute considerably less than 14, 6, and 2%, respectively, of the radiometabolite fraction. It is suggested that bioacylation of corticosterone serves to modulate the biological action of the glucocorticoid hormone on the mammary glands during lactation.

Isomer identification by kinetic energy release measurements using the voltage pulsed collision cell technique in mass-analysed ion kinetic energy spectrometry.

The voltage pulsing of the collision cell on a mass-analysed ion kinetic energy spectrometer allows simultaneous kinetic energy release measurements for unimolecular (T(V)), collision-induced (TCID(V)) and composite unimolecular and collision-induced (Tcomp(V)) decomposition processes in the time frame of a capillary gas chromatographic peak. The information gained by voltage pulsing sometimes allows more reliable isomer identification than by kinetic energy release measurements made in the non-pulsing mode alone. Presented are T(V), TCID(V) and Tcomp(V), and the ratio of their intensities for a number of isomeric halogenated compounds.

Fractionation of alkali metal cations in cationization of phthalic acid. A fast atom bombardment study.

Competition for solvent glycerol and solute phthalic acid by the alkali metal cations Li+, Na+, K+, Rb+ and Cs+ in cationization fast atom bombardment spectra is quantitated.

Dioxin in soil: bioavailability after ingestion by rats and guinea pigs.

Soil environmentally contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was given by gavage to guinea pigs and rats. The development of a characteristic clinicopathologic syndrome in guinea pigs, the induction of aryl hydrocarbon hydroxylase in rats, and the presence of TCDD in the livers of both species show that TCDD in soil exhibits high biological availability after ingestion.

Applications of isotope differentiation for metabolic studies with di-(2-ethylhexyl) phthalate.

The pervasiveness of the plasticizer di-(2-ethylhexyl) phthalate (DEHP) in the environment and especially in the laboratory results in a background that may cause severe interference with analytical studies. Animal-to-animal variability in the distribution of DEHP metabolites in excreta normally makes it necessary to use large groups of animals when different treatments are compared. Finally, radioactive tracers are usually considered undesirable for metabolic studies involving human subjects. All of these problems can be overcome through the use of multiple isotopic labels, especially 12C/13C/14C. Examples are given involving rats and monkeys, and applicability to humans is discussed. The principles involved are not limited to any particular class of test compounds. In rats, the competing pathways for metabolism of phthalate esters produce a different distribution of metabolites from a small intravenous dose of DEHP than from a large oral dose.

Identification of the metabolites of di-(2-ethylhexyl) phthalate in urine from the African green monkey.

The metabolites of di-(2-ethylhexyl) phthalate (DEHP) found in urine from African Green monkeys after intravenous administration of the 14C-labeled parent compound were isolated and identified. Criteria of identification included cochromatography with rat-derived standards on direct-phase HPLC and a variety of gas-chromatographic columns, as well as correspondence of mass spectra (70-eV electron impact and methane positive chemical ionization) with those of known standards. Approximately 80% of the urinary metabolites were excreted in the form of glucuronide conjugates. This is analogous to what has been reported for the urinary metabolites of DEHP from humans, but in clear contrast to the metabolites found in rat urine. Rat urinary metabolites of DEHP are excreted unconjugated, and consist primarily of derivatives more highly oxidized than the major metabolites produced by monkey or human. It is suggested that the African Green monkey may be a better model for human metabolism of DEHP than is the rat.

Negative ion mass spectra of some polychlorinated 2-phenoxyphenols.

Polychlorinated 2-phenoxyphenols were studied by negative ion mass spectrometry. Common to almost all of the methane enhanced negative ion mass spectra were (M-1)-, (M-36-)-., (M-37)-, (M-72)-., and chorinated quinoxide ions. The (M-36)-. ion does not apparently form in a mechanism analogous to the thermal or photochemical ring closure of these compounds to form the chlorinated dioxins. The chlorinated quinoxide ion reflects the number of chlorines on the ring with hydroxy substituent. Collision-induced dissociation mass-analyzed ion kinetic energy spectra (CID-MIKES) from different isomers were qualitatively different in both the normal and charge reversed mode of operation. Comparison of these spectra with those from other classes of polychlorinated aromatic hydrocarbons such as the dioxins or the furans may reveal a common negative ion gas phase chemistry.