Robert D.R. Parker

Hypothalamic-pituitary-adrenocortical axis activity and immune function after oral exposure to benzene and toluene

Benzene and toluene, commonly used solvents, possess neurotoxic and immunotoxic effects. Male CD-1 mice were continuously fed drinking water containing 0, 31, 166 and 790 mg/l benzene and 0, 17, 80 and 405 mg/l toluene, respectively. The concentrations of hypothalamic norepinephrine (NE) and its metabolite vanillylmandelic acid (VMA), circulating corticosterone and adrenocorticotropic hormone (ACTH), and lymphocyte-derived interleukin-2 (IL-2) activity were evaluated after 28 days of exposure to each solvent. Serum corticosterone was also measured at pretreatment, 2, 7, and 14 days of exposure. The concentrations of NE, VMA, ACTH and corticosterone were increased following exposure to these solvents. Benzene increased corticosterone levels in mice after 7 days (166 and 790 mg/l) and at 28 days (790 mg/l). Toluene elevated corticosterone levels at 14 and 28 days at the 405 mg/l exposure. IL-2 production by mouse T-lymphocytes was suppressed in the two higher benzene-treated groups, while toluene decreased IL-2 synthesis at the highest level only. Both benzene and toluene exposures stimulated hypothalamic-pituitary-adrenocortical (HPA) activity. Elevated corticosterone has been reported to inhibit IL-2 production and impair immunocompetence. Organic solvents may have, at least partially, an additive adverse effect on immune function via activated HPA status.

Toxicokinetics of nickel in rats after intratracheal administration of a soluble and insoluble form

Ninety day laboratory studies were performed to determine the whole body distribution of two chemical forms of nickel in female Wistar rats. A single injections of 15 microCi of 63Ni, either NiCl2 as a solution or NiO as a suspension, 100 nmoles in each case, was administered intratracheally. Rats were sacrificed at post-exposure intervals of 0.5, 2, and 8 hours, 1, 3, 7, 15, 30, 60 and 90 days, and major organs and tissues were analyzed for 63Ni by liquid scintillation counting technique. The soluble NiCl2 was readily distributed throughout the body, and rapidly cleared from the tissues. The insoluble NiO was distributed slowly to other organs from pulmonary tissues. The rate of decline of 63Ni from various organs in the case of NiO was similar to that of NiCl2, with notable exceptions being the lung and associated lymph nodes. After NiO administration, these organs showed a high retention of nickel after 90 days. Results indicated that Ni in soluble form was rapidly absorbed from the site of deposition following pulmonary exposure, whereas, Ni in its oxide or insoluble form was retained in lungs and related lymphatics for a considerable period. The amount of Ni in other organs following NiO exposure, though initially low in all tissues, declined in a fashion similar to organs following NiCl2 exposure. This suggests that NiO was possibly converted to a soluble form of Ni before it was translocated from lungs to other organs, and that low environmental levels of insoluble forms of nickel, which persist in the lung and lymph nodes, do have the potential for assimilation in these tissues.

Vanadium retention in rat tissues following acute exposures to different dose levels

Male Wistar rats were given vanadyl trichloride (48VOCl3) ip in doses of V ranging from 0.1 to 8 mg/kg and their tissues were collected 1 and 5 d after the injection. V was distributed in the order bone greater then kidney greater then liver greater than spleen greater than intestines greater than stomach greater than muscle greater than testis greater than lung greater than brain. Residues of V in tissues declined rapidly between 24 h and 5 d after administration. The tissue:blood ratios of V were greater than unity for bone, kidney, liver, and spleen and near unity for all other organs except the brain. Brain levels of V were found to be considerably lower than blood in all cases. V residues were linearly related to dose in most organs when the dose was below 2 mg/kg. At 8 mg/kg, however, liver and kidney showed consistently higher amounts than would be expected from the linear relationship at the low doses. Subcellular distribution of V in liver and kidney indicated that it was associated with nuclei, mitochondria, microsomes, and primarily with high-molecular-weight proteins in the soluble fraction of liver. The results suggest that the distribution pattern of V is dependent on exposure level.

Immunotoxicological evaluation of toluene exposure via drinking water in mice.

Toluene is a known contaminant found in trace amounts in groundwater. Male CD-1 mice were exposed to 0, 17, 80, and 405 mg/liter toluene in drinking water for 4 weeks. Immune function assays were selected to evaluate specific humoral and cell-mediated immunity, interleukin-2 (IL-2) activity, hematology, along with general toxicity. Toluene produced an increase in liver weight and decrease in thymus mass at the highest dose. No effects on body weights and hematological parameters, including erythrocytes, leukocytes, and their differentials were noticed. Mitogenesis by lipopolysaccharide, pokeweed mitogen, concanavalin A, and phytohemagglutinin were suppressed in splenocytes from treated mice. Splenocyte lymphoproliferation to alloantigens decreased at the 405 mg/liter concentration only. Numbers of sheep red blood cell (SRBC)-specific plaque-forming cells decreased in the highest dosed animals; however, no significant change was observed in the serum alpha-SRBC antibody level. Toluene also adversely affected IL-2 synthesis at the 405 mg/liter concentration. Findings suggest that alteration of immune functions of mice ingesting toluene was generally evident at relatively high doses, except for splenic lymphocyte responses to selected mitogens.

Subclinical effects of groundwater contaminants. III. Effects of repeated oral exposure to combinations of benzene and toluene on immunologic responses in mice.

Toxicity of environmental pollutants may be expressed as combined effects of a chemicals. Benzene, a proven hematotoxic agent, frequently occurs with toluene in cocontaminated groundwater. Groups of CD-1 male mice were exposed continuously for 4 weeks to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene (166 mg/l) + toluene (80 mg/l or 325 mg/l) in drinking water. Benzene-induced anemia was alleviated by simultaneous toluene treatment. Leukopenia and lymphopenia were observed in the case of benzene only and benzene + toluene (80 mg/l)-treated mice. The cytopenia, however, was less severe in the benzene + toluene (325 mg/l)-treated group. Immunotoxicity induced by benzene treatment alone was characterized by involution of thymic mass and suppressions of both B- and T-cell mitogeneses, mixed lymphocyte culture response to alloantigens, the tumor lytic ability of cytotoxic T-lymphocytes as determined by51Cr-release assay, and antibody production response to T-dependent antigen (sheep red blood cells). IL-2 secretion by Con A-stimulated mouse T-cells was decreased in the benzene-treated group. Toluene (325 mg/l) completely inhibited these adverse effects when it was coadministered with benzene, while the low dose of toluene (80 mg/l) did not protect against benzene-induced depressions of immune functions. Toluene administered alone at levels up to 325 mg/l showed no obvious immunotoxic effects. Results of this study demonstrated that toluene, in sufficient amounts, has an antagonistic effect on benzene immunotoxicity.

Subclinical effects of groundwater contaminants I: Alteration of and cellular immunity by benzene in CD-1 mice

Benzene is a known contaminant found in trace amounts in ground water. It has long been associated with myelotoxicity and associated immunologic effects. The present study concerned the immunotoxic potential of benzene following four weeks of continuous oral administration via drinking water at concentrations of 0, 31, 166 and 790 mg/L. Benzene-treated water produced a dose-related decrease in spleen weight and increase in kidney weight; both were significantly different at the highest level. Benzene exposure caused a significant dose-response reduction of peripheral blood leukocytes, lymphocytes, erythrocytes and resulted in a severe macrocytic anemia. Splenic lymphocyte proliferation to both B cell and T cell mitogens [lipopolysaccharide (LPS), pokeweed mitogen (PWM), concanavalin A (Con A) and phytohemagglutinin (PHA)] was followed by a dose-related biphasic responsiveness, enhanced at the lowest dose (31 mg/L) and depressed in the higher dosage groups (166 and 790 mg/L). Cell-mediated immunity as measured by mixed-lymphocyte culture (MLC) response to allogeneic cells and cytotoxic T lymphocyte (CTL) activity to YAC-1 tumor ceils exhibited similar biphasic phenomenon. Antibody production as assessed by enumeration of the sheep red blood cell (SRBC)-specific plaque-forming cells (PFC) indicated a significant suppression of PFC in animals exposed to 166 and 790 mg/L benzene. A decrease in the α-SRBC-antibody titer corresponded to the numbers of PFC. The findings suggest that oral ingestion of benzene, at the concentrations utilized, produced a biologically significant immunotoxic effect on both the humoral and cellular immune responses.

Distribution and elimination of an intratracheally administered vanadium compound in the rat

Summary Investigations were performed to determine baseline parameters for further study of the essentiality and/or toxicity of various vanadium compounds in mammals. Intratracheal injection techniques, chosen to imitate the inhalation mode of administration, and a fairly soluble form of the element, in order to maximize distribution kinetics, were selected as principal variables in the present case. 48 VOCl 3 (12.6 μCi/ml/animal) was administered intratracheally to juvenile male Wistar rats. Members randomly selected from each injection group were sacrificed at post-exposure survival times of 15 min, 4 h, 1, 7, 14, 28 and 63 days. Samples of all major organ tissues were analyzed for 48 V content by NaI(TI) gamma-ray spectroscopy. More than half of the deposited 48 V was removed from the lungs within the first day. Lung clearance rates slowed in later phases of the study with about 3% of the burden remaining after 63 days. Within 15 min of exposure, the vanadium isotope translocated to all measured organs, except the brain, with blood, heart, spleen, liver and kidneys receiving the largest fractions of the activity. Peak uptake activities for most organs occurred between 4 and 24 h after injection with the kidneys maintaining the largest fraction of 48 V in the early phases of the study. Bones accumulated activity through the first day and maintained relatively large burdens throughout the 9 week period. The testes also received small fractions of the isotope which persisted during all sacrifice intervals. The clearance of the isotope from the organs examined displayed multiple order rate kinetics. Excretion of the radiotracer occurred by both urinary and fecal means although the urinary route predominated.

Distribution and accumulation of vanadium in mice tissues

Exposure to vanadium (V), which is a toxic element widely distributed in nature, is of increasing concern because of its occurrence in various fossil fuels. The distribution of V in selected tissues of male Swiss-Webster mice was investigated at different time intervals following a single intraperitoneal dose of two mg V/kg. The highest amounts of V were observed in the kidney at one day, whereas after one day, bone showed the highest levels of all tissues. Levels of V in liver were equal to those in the kidney at two days after the administration but were significantly higher than kidney after this period. In most tissues, there was a rapid decline of V residues, which was not necessarily log-linear in fashion. The spleen showed a significant increase in V from 5 to 12 days after the administration. Groups of mice were injected intraperitoneally with doses ranging from 0.1 to 8 mg V/kg and tissues were collected after 1 and 5 days. At one day after injection, most tissues showed higher amounts of V at dose levels of 5 mg/kg than would be expected from a linear dose-dependent relationship. At 5 days, all tissues showed a linear dose-concentration relationship. The tissue: blood ratios indicated that at one day after injection there was an increased accumulation of V in tissues with increased dose. At five days after injection, the tissue:blood ratios were greater than unity for all tissues except brain. The increased accumulation of V in tissues with increased dose observed at one day was not observed at five days.

Immunological and neurobiochemical alterations induced by repeated oral exposure of phenol in mice

Phenol, a major metabolite of benzene, is a potentially immunotoxic and neurotoxic substance of environmental significance. Male CD-1 mice were continuously exposed to 0, 4.7, 19.5, and 95.2 mg phenol/l in drinking water for 4 weeks. Various immune functions were evaluated and levels of selected neurotransmitters and metabolites measured in discrete brain regions. The doses of phenol did not produce any overt clinical signs of toxicity; peripheral red blood cell counts and hematocrits decreased. A dose of 95.2 mg/l suppressed the stimulation of cultured splenic lymphocytes by lipopolysaccharide, pokeweed mitogen, and phytohemagglutinin and the response in mixed lymphocyte cultures. The two high doses suppressed antibody production response to the T cell-dependent antigen (sheep erythrocytes), as determined by plaque-forming cells, and serum antibody levels. Mice treated with phenol had lower levels of neurotransmitters in several brain regions. In the hypothalamus, a major norepinephrine-containing compartment, the concentrations of norepinephrine significantly decreased by 29 and 40% in groups dosed with 19.5 and 95.2 mg/l, while dopamine concentrations decreased in the corpus striatum by 21, 26, and 35% at 4.7, 19.5 and 95.2 mg/l, respectively. Phenol also decreased 5-hydroxytryptamine in the hypothalamus, medulla oblongata, midbrain and corpus striatum. Levels of monoamine metabolites decreased in the hypothalamus (5-hydroxyindoleacetic acid), midbrain (vanillylmandelic acid), corpus striatum (vanillylmandelic acid and dihydroxyphenylacetic acid), cortex (vanillylmandelic acid), and cerebellum (dihydroxyphenylacetic acid).

Subclinical effects of groundwater contaminants. II. Alteration of regional brain monoamine neurotransmitters by benzene in CD-1 mice

Benzene, a common groundwater contaminant, possesses neurotoxic and behavioral effects. Male, adult CD-1 mice were continuously fed drinking waterad libitum containing 0, 31, 166 and 790 mg/L benzene for four weeks. Endogenous levels of the catecholamines norepinephrine (NE) and dopamine (DA), the catecholamine metabolites 3-methoxy-4-hydroxymandelic acid (VMA), 3,4-di-hydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the indoleamine serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), were measured by high-performance liquid chromatography (HPLC) in six discrete brain regions. In the hypothalamus, the brain region richest in NE, concentrations of NE increased by 40, 58 and 61% when mice received doses at 31, 166 and 790 mg/L, respectively. Significant increases of NE were also observed in the medulla oblongata and cerebellum. Dopamine concentrations increased significantly in the hypothalamus and corpus striatum. Increases of catecholamine metabolites were seen in a number of brain regions: midbrain (DOPAC), corpus striatum (VMA, DOPAC, HVA), cerebral cortex (VMA) and cerebellum (VMA). Benzene ingestion significantly increased 5-HT concentrations in the hypothalamus, corpus striatum, midbrain, cerebral cortex and medulla oblongata. Concomitant with increases of 5-HT, 5-HIAA increased in corpus striatum, midbrain, cerebral cortex and medulla oblongata. The findings indicate that oral ingestion of benzene by CD-1 mice induced both synthesis and catabolism of the monoamine neurotransmitters investigated.