The subchronic oral toxicity of the beta-isomer of hexachlorocyclohexane in rats.

The 13-week oral toxicity of beta-HCH, a non-pesticidal isomer of hexachlorocyclohexane, was investigated in rats with doses of 0, 2, 10, 50, or 250 mg/kg feed. Parameters studied comprised clinical signs, growth and food intake, biochemistry, hematology, organ weights, and histopathology. In all dose groups liver effects comprising increase of organ weight, centrilobular hepatocytic hypertrophy, and proliferation of smooth endoplasmic reticulum or increased activity of microsomal enzymes, were observed. In the 50 mg/kg group the weights of thymus and testes were affected. In the highest dose group, progressive clinical signs leading to the unscheduled sacrifice of approximately 50% of the rats were observed. Moreover, in the males of this group atrophy of the testes, characterized by a reduced size of the seminiferous tubules and a decreased number of interstitial cells was observed in association with spermatogenic arrest. The females in this group showed atrophy of the ovaries with impaired oogenesis and focal hyperplasia and metaplastic changes of the endometrial epithelium. These effects are discussed with respect to a possible estrogenic action of beta-HCH.

Effect of triphenyltin hydroxide on the immune system of the rat.

To evaluate the functional significance of triphenyltin hydroxide (TPTH)-induced lymphopenia and lymphocyte depletion in thymus-dependent areas of spleen and lymph nodes, various immune function studies were carried out after 3 or 4 weeks TPTH exposure. Weaned male rats were fed a diet containing 25 mg TPTH/kg, a concentration that did not influence food intake and weight gain. TBTO exposure was continued during the course of the function tests. As parameters of the cell-mediated immunity in 2 experiments the delayed-type hypersensitivity reactions to ovalbumin and tuberculin were significantly suppressed. No effect was observed on allograft rejection, splenic clearance of Listeria monocytogenes at days 5 and 6 after infection, and responsiveness of thymocytes to different T-cell mitogens. In contrast, the response of splenic lymphocytes to the T-cell mitogen phytohaemagglutinin was significantly suppressed. As TPTH treatment reduced the number of spleen cells, mitogenic response calculated per whole spleen was significantly depressed. Regarding the humoral immunity, no effect was observed on serum IgM and IgG levels, on the thymus-independent IgM response to E. coli lipopolysaccharide (LPS), and on the primary and secondary IgM and IgG response to the thymus-dependent antigen tetanus toxoid. Also, no effect was found on phagocytic and killing capacity of macrophages as demonstrated by unaltered splenic clearance of L. monocytogenes at days 1 and 2 after infection. Slightly enhanced mortality of TPTH-treated animals was observed in a L. monocytogenes mortality assay. Finally, TPTH did not increase the susceptibility of rats to endotoxin (LPS).

Toxicity of sodium bromide in rats: effects on endocrine system and reproduction.

Bromide has a low acute oral toxicity, with LD50 values in rodents ranging from 3500 to 7000 mg/kg body weight. It is rapidly absorbed and steady-state serum levels have been reached in rats within 4 weeks. The biological half-life of bromide, and consequently the serum levels, are strongly dependent on chloride intake. Feeding of sodium bromide to rats for 90 days in concentrations of 0, 75, 300, 1200, 4800 and 19,200 mg/kg diet led to a complex of changes in the endocrine system, thyroid activation being the most prominent. Furthermore, in the highest dose groups a decrease in spermatogenesis in the testes and decreased secretory activity of the prostate or a reduction in the number of corpora lutea in the ovaries were found. A three-generation reproduction study of the same dietary concentrations showed in the two highest dose groups a decrease in fertility which appeared to be reversible upon bromide withdrawal. Macroscopically, no changes in the offspring were observed. From these studies a no-effect level for bromide ion of 240 mg/kg diet was determined, corresponding to a tentative Acceptable Daily Intake (ADI) of 0.12 mg/kg body weight. This is in good agreement with a preliminary ADI of 0.1 mg/kg established in an experiment with human volunteers, but is considerably lower than the ADI of 1 mg/kg estimated by FAO/WHO. It is suggested that bromide exerts an inhibitory effect on the thyroid, resulting in an increased hormonal stimulation of this organ by the pituitary gland.

The influence of sodium bromide in man: a study in human volunteers with special emphasis on the endocrine and the central nervous system.

Sodium bromide was administered orally in capsules to healthy volunteers in doses of 0, 4 or 9 mg Br-/kg/day using a double-blind design. Each treatment was given to seven males for 12 weeks and to seven non-pregnant females (not using oral contraceptives) over three full cycles. Special attention was paid to possible effects on the endocrine and central nervous systems. At the start and end of the study, a full medical history, the results of a physical examination, haematological studies and standard clinical chemistry and urine analyses were recorded for each subject. These showed no changes for individuals following treatment, except for some incidence of nausea associated with bromide-capsule ingestion. Mean plasma-bromide concentrations at the end of treatment were 0.08, 2.14 and 4.30 mmol/litre for males and 0.07, 3.05 and 4.93 mmol/litre for females of the 0-, 4- and 9-mg Br-/kg/day groups, respectively. Plasma half-life was about 10 days. In the females taking 9 mg Br-/kg/day (but in no other group) there was a significant (P less than 0.01) increase in serum thyroxine and triiodothyronine between the start and end of the study but all concentrations remained within normal limits. No changes were observed in serum concentrations of free thyroxine, thyroxine-binding globulin, cortisol, oestradiol, progesterone or testosterone, or of thyrotropin, prolactin, luteinizing hormone (LH) and follicle-stimulating hormone before or after the administration of thyrotropin-releasing hormone and LH-releasing hormone. Analysis of neurophysiological data (EEG and visual evoked response) showed a decrease in delta 1- and delta 2-activities and increases in beta-activities and in mean frequency (Mobility parameter) in the groups on 9 mg Br-/kg/day, but all the findings were within normal limits.

Study of sodium bromide in human volunteers, with special emphasis on the endocrine system.

1 Bromide, 1 mg kg-1 daily, was administered to 21 healthy volunteers (11 females not using oral contraceptives and not pregnant and 10 males, during 8 weeks or 2 full cycles to determine whether ingestion of a dose equal to the acceptable daily intake might induce effects. Special attention was paid to the endocrine system because endocrine changes were predominant in rats receiving sodium bromide (NaBr) in their diets. 2 There was no difference between the results of a full medical history and physical examination at the start and at the end of the experiment. 3 The results from the measured haematological, biochemical and urine analyses did not change during the experiment. 4 In females the plasma bromide concentration rose from 0.08 +/- 0.01 mmol 1(-1) to 0.97 +/- 0.18 mmol 1(-1) and in males from 0.08 +/- 0.01 mmol 1(-1) to 0.83 +/- 0.09 mmol 1(-1) (mean +/- s.d.). 5 No changes were observed in the serum concentrations of thyroxine, free thyroxine, thyroxin binding globulin, triiodothyronine, cortisol, testosterone, estradiol and progesterone. Also no changes were observed in the serum concentrations of thyroid stimulating hormone (TSH), prolactin, luteinizing hormone (LH) and follicle stimulating hormone (FSH) before and after the administration of thyroid stimulating hormone releasing hormone (TRH) and luteinizing hormone releasing hormone (LHRH).

Acute oral toxicity of inorganic cobalt compounds in rats.

Eight cobalt compounds were administered to rats by gastric intubation, and the following LD50 values (in mg anhydrous compound/kg body weight) were determined: cobalt(II) fluoride 150, cobalt(II) oxide 202, cobalt(II) phosphate 387, cobalt(II) bromide 406, cobalt(II) chloride 418, cobalt(II) sulphate 424, cobalt(II) nitrate 434 and cobalt(II) acetate 503. After administration of the cobalt compounds, body temperatures decreased by 2.5-7.5 degrees C. The liver, heart and kidneys of rats given cobalt(II) fluoride or oxide were examined microscopically. Hyperaemia, haemorrhage and cytoplasmic changes were noted, while the kidney glomeruli were very rich in cells and basal membranes were thickened. Cells of the proximal tubules were swollen and showed vacuolization and degeneration. In the hearts of some rats proliferative and oedematous interstitial tissue and swollen muscle fibres were observed, and focal degeneration, vacuolization and necrosis associated with disappearance of the cross striations were also noted.

[Toxicological aspects of the use of hormones as anabolic agents (author's transl)]. / Toxicologische aspecten van het gebruik van hormonen als anabolica.

The use of anabolic agents may give rise to residues in foods of animal origin and thus to potential effects on public health. Therefore, the physiology, metabolism and toxicity of the three endogenous hormones. 17 beta-oestradiol, progesterone and testosterone are discussed. In addition, the effects of the use of three exogenous hormones, diethylstilboestrol (DES), trenbolone and zeranol are evaluated. As can be expected all six compounds have effects on the endocrine system and reproduction. Endogenous hormones and DES are teratogenic at high-dose levels. With the exception of DES, there is no evidence of a mutagenic action. 17 beta-Oestradiol and testosterone were shown to induce tumours at high-dose levels in experimental animals; probably however, a threshold can be established. The residues in edible tissue resulting from the use of endogenous hormones are much smaller than are the natural levels in cow's milk and butter. In view of the carcinogenicity of DES in man, its use should be strongly discouraged. A definite statement on the acceptability of the use of trenbolone and zeranol cannot be made.

The influence of malnutrition on the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rats.

A single oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (20 or 40 microgram/kg body wt) administered to rats resulted in reduced body weight gain, water intake, degenerative changes in the liver and involution of the thymus. Although a restricted diet alone caused thymic involutions it was shown that TCDD at 10 or 20 microgram/kg body wt accentuated this atrophy. Microscopically, a marked atrophy of the thymus and swelling and necrosis of the liver were found in the malnourished animals. The effects of TCDD were also tested in rats fed either 3.5%, 26% or 55% protein. There was no clear relation between the protein level and the influence of TCDD on the thymus. However, the effect of TCDD on body weight and the liver was more severe in rats given low protein diet. These effects were not reversed by high protein diet. Since it is unlikely that the influence of TCDD on the thymus is related to malnutrition, other mechanisms, such as depletion of energy reserves, a direct effect of TCDD on the thymus or a mediation by the hepatotoxic action may be involved.

Role of the endocrine system in the action of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the thymus.

Several experiments were conducted to study the involvement of the adrenal and the pituitary gland in the acute toxic effects of TCDD. Adrenalectomized or hypophysectomized rats were treated with a single oral dose of 10 or 20 microgram of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)/kg body weight. The reduced growth rate, the hepatotoxic effects and thymic involution induced by TCDD were not prevented by the adrenalectomy. The pituitary gland did not appear to be involved in causing thymic involution. In fact, the thymic effects of TCDD intoxication were even somewhat increased in hypophysectomized rats. Treatment with growth hormone failed to prevent thymic involution or the influence of TCDD on the liver.

Hexachlorobenzene-induced stimulation of the humoral immune response in rats.

Rats were fed diets containing 0, 500, 1000, and 2000 mg HCB/kg during a 3-week period. Marked weight increases of spleen, popliteal and mesenteric lymph nodes and of the liver were found. Histologically, the white pulp in the spleen was enlarged because of an increase in size of marginal zones and follicles. In addition, there was an increase of extramedullary hemopoiesis. In the lymph nodes, the number of high endothelial venules was increased at all dose levels. The number of neutrophils, basophils and monocytes in the peripheral blood was significantly increased, whereas peripheral lymphocyte counts were slightly higher. Total serum IgM levels were markedly increased, but IgG concentrations were unaltered. On the basis of this experiment, the 1000 mg HCB/kg diet level was chosen for the different function studies that were carried out after a 3-weeks dietary regimen. Regarding the humoral immunity, IgM antibodies to LPS were unaltered, whereas primary and secondary IgM and IgG antibody titers to tetanus toxoid were increased approximately three-fold. HCB did not significantly alter the cell-mediated immunity, as shown by the following parameters: resistance to Listeria monocytogenes infection, rejection of skin transplants, and delayed-type hypersensitivity to tuberculin. The phagocytizing capacity of macrophages was studied by measuring the blood clearance of carbon particles. HCB did slightly depress the phagocytic index, but the difference with control animals was statistically not significant. The in vitro responsiveness of thymus cells to the mitogens PHA, Con A, and PWM was not changed by in vivo HCB-treatment. On a cell-for-cell basis, the responsiveness of spleen cells was increased when cultured in the presence of LPS. On a whole organ basis, the response to PHA, Con A, PWM, and LPS was markedly enhanced because of an increase in the number of nucleated spleen cells. Regarding peripheral lymphocytes, only the response to the mitogen Con A was higher. On the basis of these studies it is concluded that HCB stimulates the humoral immune response in the rat, enhances the in vitro responsiveness of spleen cells to the different mitogens mainly as a result of an increase in the number of splenic lymphocytes, but does not alter the cell-mediated immunity as shown with in vivo tests. This result contrasts with data in the literature that show that HCB suppresses the humoral and cell-mediated immunity in mice. Finally, HCB pretreatment only marginally increased the susceptibility of rats to endotoxin, whereas mice have been shown to be 20-fold more susceptible to the lethal effects of bacterial endotoxin.

Effect of food deprivation on low level hexachlorobenzene exposure in rats.

The purpose of the present study was to determine if food deprivation could modify the biological activity of hexachlorobenzene (HCB) in the rat. Male and female Wistar rats were divided into 6 groups containing 6 animals. Groups 1, 3 and 5 were fed standard control diet ad libitum for 2 weeks. For the next 4 weeks their respective diets contained 0, 20 and 100 ppm HCB. Groups 2, 4 and 6 were also fed a standard control diet for 2 weeks but at an intake of approximately 50% of those groups fed ad libitum. For the following 4 weeks food deprivation was continued but the control diets were replaced with diets containing 0, 40 or 200 ppm HCB. The parameters measured were food, body weight changes, changes in tissue weights, microsomal enzyme activity and histopathology of liver, kidneys, adrenals and pancreas. Tissue residue profiles were established for plasma, liver, brain and adrenals. Food deprivation augmented the induction of microsomal enzyme activity by HCB in both males and females at both dose levels. Liver hypertrophy was observed in both males and females fed 200 ppm HCB and subjected to food libitum. Food deprivation resulted in a higher plasma, liver, brain and adrenal accumulation of HCB in both males and females.

[Methods for assessing permissible levels of intentional and unintentional food additives (author's transl)]. / Wijze van vaststellen van de toelaatbare gehaltes aan gewenste of ongewenste toevoegingen in voedingsmiddelen

Foods may contain intentional and unintentional additives. The former group includes, for example, flavours, colouring substances and preservatives, while the latter includes pesticides and mycotoxins. To determine the amount of these substances that are admissible in man, extensive toxicological tests have to be performed with experimental animals to establish a no toxic effect level. Based on the no toxic effect level and applying a safety factor an "acceptable daily intake" (ADI) can be calculated for human beings. The problems outlined in the article are illustrated by several examples, such as the presence of DDT and aflatoxin M1 in milk and of mercury in fish.