Journal of Toxicology and Environmental Health

Kanja, Laetitia; Skåre, Janneche Utne; Nafstad, Inger; Maitai, Charles K.; Løkken, Per

doi: 10.1080/15287398609530944pmid: 3783766

Residue levels of the chlorinated hydrocarbons p,p'‐DDT (2,2‐bis(p‐chlorophenyl)‐1,1,1‐trichloroethane), p,p'‐DDE (2,2‐bis(p‐chlorophenyl)‐1,1 ‐dichloraethane), hexa‐chlorobenzene (HCB), α‐, β‐, and y‐hexachlorocyclohexane (HCH), aldrin, dieldrin, and polychlorinated biphenyls (PCBs) were determined in human milk of Kenyan mothers living in different areas of Kenya. The main organochlorine contaminants found in all the milk samples analyzed were p,p'‐DDT and p,p'‐DDE. Great regional differences were found, and mean levels of sum DDT and DDT/DDE ratio ranged from 1.1 to 18.7 mglkg milk fat and from 0.7 to 5.7, respectively. In general, relatively low residue levels of HCB, α‐HCH, β‐HCH, aldrin, and dieldrin were detected in 59, 37, 27, 37, and 19%, respectively, of all the milk samples analyzed. Quantifiable residue levels of PCBs and α‐HCH were not found. The results were examined in relation to differences in living conditions with regard to agricultural activities, dietary habits, and reported use of pesticides in the various sampling areas.

Thomas, I. K.; Koizumi, A.; Imamura, T.

doi: 10.1080/15287398609530945pmid: 3491217

The effect of O,O‐dimethyl, S‐ethyl phosphorothioate (OO‐Me S‐Et) on macrophage function and the responses of T‐ and B‐cells of the immune system were investigated using an in vitro model. The role of glutathione (GSH) enhancement of OO‐Me S‐Et suppression of immune responses was studied after either direct culturing with spleen or B‐cells alone or coculture of B‐cells with either B‐ or T‐cells with or without preincubation with OO‐Me S‐Et and glutathione enriched cytosol. The results indicated that OO‐Me S‐Et, when preincubated with CSH, suppresses immune responses through an inhibition of B‐ and T‐cell functions. Both cytotoxic T‐lymphocyte (CTL) generation and antibody production were impaired. In mixing experiments of pre‐treated and normal cells, the inhibitory effect was also observed on macrophages and helper T‐cells responding to a T‐dependent antigen. It appears that the immunosup‐pressive effect of OO‐Me S‐Et is due to impairment of collaboration of T‐ and B‐cells, i.e., mainly due to impairment of T‐cell functions. The immunotoxic effect was only detectable when glutathione was present in the preincubation mixture.

Linder, Ralph E.; Hess, Rex A.; Strader, Lillian F.

doi: 10.1080/15287398609530946pmid: 3783767

Weanling male Sprague‐Dawley rats were gavaged 5 d/wk with 1,3‐dinitrobenzene (m‐DNB) at dosages of 0, 0.75, 1.5, 3.0, and 6.0 mg/kg • d. Males were bred to untreated females during treatment wk 10 and were killed during treatment wk 12. Although males dosed with 3 mg/kg • d inseminated the females and evidence of mating was observed in males dosed with 6 mg/kg • d, none of the males in these groups sired litters. Diminished sperm production (reduced testicular sperm head counts), decreased cauda epididymal sperm reserves, nonmotile spermatozoa, atypical sperm morphology, decreased weights of the testes and epididymides, seminiferous tubular atrophy, and incomplete spermatogenesis were also observed in these groups. Sperm production was also decreased in males dosed with 1.5 mg/kg • d. Changes in the spleen included increased weight at dosages of 1.5 mg/kg • d or higher and splenic hemosiderosis, which ranged from slight in rats treated with 0.75 mg/kg • d to moderately severe in those dosed with 6 mg/kg • d. The data indicate that m‐DNB is a potent testicular toxicant in the male rat, capable of producing extensive damage to reproductive tissues and reproductive failure. Limited data on four rats that received 6 mg/kg • d and were allowed a 5‐mo posttreatment recovery period suggested that the testicular effects are at least partially reversible.

El Dareer, Salah M.; Kalin, Jack R.; Tillery, Kathleen F.; Hill, Donald L.

doi: 10.1080/15287398609530947pmid: 3783768

Administration to rats of oral doses of [ 14 C]‐2‐hydroxy‐4‐methoxybenzophenone (HMB) in the range of 3.01–2570 mg/kg revealed that a dose‐dependent elimination process was operative at the highest dose. Urinary excretion (63.9–72.9% of the dose in 72 h) was the major route for elimination of radioactivity. An intravenous dose (4.63 mg/kg) distributed rapidly throughout the body of rats and appeared in the urine in an amount (67.4%) similar to those for the oral doses. Rats absorbed large portions of doses of [ 14 C]HMB administered topically, either as an ethanolic solution (50, 200, or 800 μg/rat) or formulated in a lotion (50 μg/rat). For rats with biliary cannulas, 36.6% of the radioactivity of an intravenous dose (4.46 mg/kg) appeared in the bile in 4 h; the initial half‐life for biliary elimination was 40 min. In the bile, at least five radioactive components, none of which was intact HMB, were present. The two major components were glucuronides of HMB and demethylated HMB, and a third was probably a sulfate ester of hydroxylated HMB. In urine, there were nine radioactive components, two of which were unchanged HMB and its glucuronide.

Miller, George E.; Brabec, Michael J.; Kulkarni, Arun P.

doi: 10.1080/15287398609530948pmid: 3537323

It is not clear whether glutathione (CSH) conjugation to 1,2‐dibromo‐3‐chloropro‐pane (DBCP) results in genotoxic activation. Therefore S9, cytosolic, and microsomal fractions from uninduced rat liver were evaluated for their relative ability to activate DBCP in a modified Ames system. The S9 enzymes, either alone or in combination with exogenous CSH, did not enhance the mutagenicity of DBCP; identical results were obtained with cytosolic enzymes. Significant mutagenic activation of DBCP was produced by either S9 or microsomal fractions in the presence of NADPH. Activation was proportional to cytochrome P‐450 concentrations, and was diminished by exogenous GSH. The protection against genotoxicity exerted by CSH did not require cytosolic glutathione S‐transferases (GST). Thus, mutagenic activation of DBCP as obtained with S9 fractions is primarily due to biotransformation by microsomal rather than by cytosolic enzymes. Kinetic studies of cytosol‐catalyzed conjugation of CSH to DBCP revealed tissue‐specific differences in apparent Km and Vmax. Renal and tes‐ticular CSTs were associated with 28–46% smaller Vmax values when compared to hepatic CSTs (31.2 ± 7.9 nmol/min • mg protein). However, renal and testicular GSTs had relatively higher affinities for DBCP. Thus, extrahepatic tissues possess significant capacity to conjugate CSH to DBCP. DBCP‐CSH conjugates may undergo enzymatic modification by extrahepatic peptidases and β‐lyase to yield other sulfur‐containing moieties that perhaps mediate DBCP's extrahepatic toxicity.

Millner, Glenn C.; Fu, Peter P.; Cerniglia, Carl E.

doi: 10.1080/15287398609530949pmid: 3783769

The fungal metabolism of the potent mutagenic and carcinogenic nitropolycyclic aromatic hydrocarbon (nitro‐PAH) 6‐nitrobenzo[a]pyrene (6‐NO 2 ‐BaP) was investigated. Cunninghamella elegans was incubated with 6‐NO 2 ‐BaP for periods ranging between 1 and 7 d, and the metabolites formed were separated by high‐performance liquid chromatography and identified by their UV‐visible absorption, mass, and 1 H nuclear magnetic resonance spectra. The results of our study indicate that C. elegans metabolized 6‐NO 2 ‐BaP to glucoside and sulfate conjugates of 1‐ and 3‐hydroxy 6‐NO 2 ‐BaP and suggests that glycosylation and sulfation reactions may represent detoxification pathways in the fungal metabolism of nitro‐PAHs. Experiments using [C‐ 3 H]‐6‐NO 2 ‐BaP indicated that C. elegans metabolized 62% of 6‐NO 2 ‐BaP within 768 h. Our data also indicated that the nitro group at the C‐6 position of benzo[a]pyrene blocked metabolism at the regions peri to the nitro substituent (C‐7, C‐8 positions) and enhanced metabolism at the C‐l and C‐3 positions. The ability of the fungus C. elegans to metabolize 6‐NO 2 ‐BaP to biologically inactive compounds may have practical applications in the detoxification of nitro‐PAH‐contaminated wastes.

Greenman, David L.; Fullerton, Floyd R.

doi: 10.1080/15287398609530950pmid: 3783770

Female BALB/c and B6C3F1 mice were examined after a 3‐wk exposure to dietary estradiol (0, 400, 800, 1600, and 3200 ppb) in a purified diet (AIN‐76A) or a natural‐ingredient diet (NIH‐07). Histological findings, which became more prevalent with increasing estradiol dosage in both mouse genotypes, included vaginal hyperkeratosis and mucoid stroma, uterine inflammation, hydrometra and glandular hyperplasia, and ovarian corpora lutea depletion. At the two lower doses of estradiol, responses were generally more prevalent or severe in mice fed the purified diet than in those fed the natural‐ingredient diet. However, in BALB/c mice, several responses to the two higher estradiol doses were greater when estradiol was given in the natural‐ingredient diet rather than in the purified diet. These responses included corpora lutea depletion, vaginal hyperkeratosis, and uterine inflammation and hydrometra. In B6C3F1 mice, most responses to estradiol at concentrations of 400, 800, and 1600 ppm were more prevalent or severe in mice fed the purified diet than in those fed the natural‐ingredient diet. It can be concluded that several responses to estradiol in mice maintained for a 3‐wk period on a purified diet differed significantly from mice maintained on a natural‐ingredient diet.

Kraus, A. L.; Bernstein, I. A.

doi: 10.1080/15287398609530951pmid: 3023648

Removal from adipose tissue is an important first step in ultimate removal of many lipophilic xenobiotics from the body. This study concerned the elucidation of mechanisms by which hexabromobiphenyl (HBB) was deposited in and removed from adi‐pocytes. Adipocytes derived from the 3T3L1 cell line of mouse fibroblasts were used to conduct studies in vitro. Results support the idea that HBB enters the 3T3L1 adipocyte via passive diffusion. A plot of the velocity of uptake versus concentration was linear, the uptake of HBB does not appear to be energy dependent, and structurally similar biphenyls did not cause an inhibition of uptake. A linear relationship between the quantities of triglyceride and HBB in the cells was found during both uptake of HBB in lipogenesis and removal of HBB in lipolysis (r > 0.98). This supports the contention that the quantity of triglyceride in the cells has a strong influence on the movement of HBB between adipocytes and surrounding pseudoblood. Evidence has been presented that is consistent with the hypothesis that HBB moves freely across the adipocyte membrane and is sequestered in either cells or medium according to its relative solubility in these compartments. Methods to increase the removal of HBB from adipocytes have been proposed.

Rietjens, I. M. C. M.; Poelen, M. C. M.; Hempenius, R. A.; Gijbels, M. J. J.; Alink, G. M.

doi: 10.1080/15287398609530952pmid: 3783771

The toxicity of ozone and nitrogen dioxide is generally ascribed to their oxidative potential. In this study their toxic mechanism of action was compared using an intact cell model. Rat alveolar macrophages were exposed by means of gas diffusion through a Teflon film. In this in vitro system, ozone appeared to be 10 times more toxic than nitrogen dioxide. α‐Tocopherol protected equally well against ozone and nitrogen dioxide. It was demonstrated that α‐tocopherolprovided its protection by its action as a radical scavenger and not by its stabilizing structural membrane effect, as (1) concentrations of a‐tocopherol that already provided optimal protection against ozone and nitrogen dioxide did not influence the membrane fluidity of alveolar macrophages and (2) neither one of the structural α‐tocopherol analogs tested (phytol and the methyl ether of a‐tocopherol) could provide a protection against ozone or nitrogen dioxide comparable to the one provided by a‐tocopherol. It was concluded that reactive intermediates scavenged by a‐tocopherol are important in the toxic mechanism of both ozone and nitrogen dioxide induced cell damage. However, further results presented strongly confirmed that the kind of radicals and/or reactive intermediates, and thus the toxic reaction mechanism involved, must be different in ozone‐ and nitrogen dioxide‐induced cell damage. This was concluded from the observations that showed that (1) vitamin C provided significantly better protection against nitrogen dioxide than against an equally toxic dose of ozone, (2) glutathione depletion affected the cellular sensitivity toward ozone to a significantly greater extent than the sensitivity towards nitrogen dioxide, and (3) the scavenging action of α‐tocopherol was accompanied by a significantly greater reduction in its cellular level during nitrogen dioxide exposure than during exposure to ozone. One of the possibilities compatible with the results presented in this study might be that lipid (peroxyl) free radicals formed in a radical‐mediated peroxidative pathway, resulting in a substantial breakdown of cellular α‐tocopherol, are involved in nitrogen dioxide‐induced cell damage, and that lipid ozonides, scavenged by a‐tocopherol as well, are involved in ozone‐induced cell damage.

Whaley, Sandra L.; Wolff, Ronald K.; Muggenburg, Bruce A.; Snipes, Morris B.

doi: 10.1080/15287398609530953pmid: 3783772

In this study, the retention and clearance of particles instilled onto the epithelium at two sites in the nasal cavity were examined. Polystyrene microspheres (3 μm geometric diameter) were labeled with 141 Ce or 85 Sr and instilled simultaneously on the maxillary and ethmoid turbinates of beagle dogs. The retention and clearance patterns of the microspheres were followed for 30 d after instillation. Tissue samples, excreta content, and autoradiography of the radiolabels provided the basis for defining the fate of the microspheres or the radiolabels dissolved from the microspheres. Early nasal mucus velocity was significantly faster (p < 0.05) from the maxillary turbinate region (2.5 ± 0.7 mmlmin, mean ± SE) than from the ethmoid turbinate region (0.6 ± 0.4 mmlmin). Retention at both instillation sites at 30 d after instillation was approximately 0.7% of the amount initially instilled. Radioactivity was excreted primarily via the feces during the first few days. Radiolabel measured in urine and tissues other than turbinates was small (<0.05% of the initial burden), indicating minimal dissolution of the radiolabel from the particles. Autoradiographs of turbinate tissue revealed particles sporadically located in the epithelial submucosa. From these data, it was concluded that a significant difference in early clearance for particles exists between the ethmoid and maxillary turbinates, but there was no difference in the fraction of particles retained in these two areas for long periods of time.