Study of general toxic and organotropic properties of ampicillin combined with sulbactam]

The effect of sulacillin, a combination of sulbactam and ampicillin (1:2), on the functions of the liver and kidneys, peripheral blood count, cardiovascular and central nervous systems was studied in acute and chronic experiments on animals of various species. The allergenic and local irritating properties of the combination were also studied. It was shown that the combination was low toxic and the interaction of sulbactam and ampicillin by the lethal effect was additive. When the combination was administered intravenously to mice, its LD50 amounted to 6 g/kg. In chronic experiments on rats parenterally given the combination in doses equivalent to the therapeutic ones there were no changes in the examined systems and organs. When used in the doses exceeding the therapeutic ones, sulacillin used during long periods induced a transitory elevation of blood levels of transaminases and alkaline phosphatases, an increase in the relative weight of the liver and kidneys, elongation the typhlon and an increase in glycogen levels in the hepatocytes without morphological changes. The combination had no significant effect of sulacillin and the painful injections alleviated by local anesthesia were recorded. The allergenic properties of the combination were moderate and did not differ from those of ampicillin. The data indicate that the combined sulacillin preparation greatly resembles its foreign analogue.     

Chronic oral administration of raw garlic protects against isoproterenol-induced myocardial necrosis in rat

Wistar albino rats (150-200 g) were fed raw garlic homogenate orally in three different doses (125, 250, 500 mg/kg/day) for 30 days. Isoproterenol (85 mg/kg, s.c. 2 doses at 24-h interval, animals sacrificed after 24 h of last injection) induced myocardial necrosis in control rats and after 30 days of garlic feeding. Myocardial oxidative stress was evident following isoproterenol administration by reduction in myocardial superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities along with a rise in plasma thiobarbituric acid reactive substances (TBARS). Myocardial necrosis was evident from the light microscopic and ultrastructural changes, along with a rise in plasma lactate dehydrogenase (LDH). Significant preservation of myocardial SOD activity was observed in all the garlic-fed rats. However, there was no significant change in myocardial reduced glutathione level and GPx activity in any of the treated groups. Significant reduction in plasma TBARS and LDH levels was observed in the 500 mg/kg garlic treated group. Isoproterenol-induced myocardial morphological changes were least in the 250 and 500 mg/kg garlic treated groups. The results suggest that chronic oral administration of raw garlic offered protection against isoproterenol-induced myocardial necrosis and associated oxidative stress.     

虫草发酵菌丝体对胰岛素抵抗大鼠氧化应激的缓解作用

探究虫草发酵菌丝体对胰岛素抵抗(IR)大鼠氧化应激的影响。采用低中高剂量虫草发酵菌丝体(剂量分别为1.65g/kg饲料,3.30g/kg饲料和6.60g/kg饲料)分别干预IR大鼠。口服葡萄糖耐量实验观察不同剂量虫草发酵菌丝体的降糖效果,同时观察血脂、氧化应激水平的变化情况。RT-PCR法测肌肉、肝脏组织氧化应激相关基因Nrf2、HO-1和NQO1mRNA相对表达量,Westernblot法测其蛋白相对表达量。结果发现CM干预能够显著改善IR大鼠空腹血糖、血脂和机体氧化应激水平,肌肉、肝脏组织Nrf2、HO-1和NQO1mRNA相对表达量显著上升,肝脏Nrf2和NQO1蛋白相对表达量显著上调,并且具有剂量依赖性。说明CM具有缓解IR大鼠氧化应激的作用。     

Effect of Withania somnifera Dunal in ethanol-induced anxiolysis and withdrawal anxiety in rats

Withania somnifera (WS) or its psychotropic preparation is known to play a critical role in morphine, alcohol and benzodiazepines addiction. This study investigates the role of WS in acute ethanol and withdrawal from chronic ethanol consumption using elevated plus maze paradigm in rats. Acute administration of ethanol (1.5-2 g/kg, ip) triggered anxiolytic effect and withdrawal from prolonged ethanol (9% v/v ethanol, 15 days) consumption elicited enhanced behavioral despair (anxiety). Acute administration of WS (50 mg/kg, oral) potentiated the anxiolytic action of subeffective dose of ethanol (0.5 or 1 g/kg, ip). Moreover, the ethanol withdrawal anxiety was markedly antagonized in dose dependent manner by WS at 200 and 500 mg/kg or higher dose of ethanol (2.5 g/kg). However, co-administration of subeffective doses of WS (50 mg/kg, oral) and ethanol also attenuated withdrawal-induced anxiety due to chronic ethanol (9% v/v ethanol, 15 days) consumption. The results suggest the protective effect of WS in the management of ethanol withdrawal reactions.     

Toxicity of pure alkaloid of Tylophora asthamatica in male rat

Administration of pure alkaloid of T. asthamatica, suspended in peanut oil and given in single doses (12-100 mg/kg) by gavage, to male rats caused inactivity, respiratory distress, salivation, nasal discharge and diarrhoea. The oral LD50 value of the alkaloid was 35.32 mg/kg. In short term toxicity study daily doses of the alkaloid (1.25, 2.5, 5 and 10 mg/kg) were given to male rats for 15 days. Smaller doses of the alkaloid (1.25 and 2.5 mg/kg/day) produced no signs of poisoning or death in animals; while 5 mg/kg/day produced signs of poisoning and death of two animals, 10 mg/kg/day caused death of all the animals within 7 days. Activities of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alkaline phosphatase were significant and associated with morphological changes in liver. The alkaloid also caused marked changes in the morphology of seminiferous tubules and spermatogenic activity of experimental animals. Since the alkaloid is effective in microgram quantities, the non toxic effects observed after daily doses of 1.25 mg/kg in male rats assume great therapeutic significance.     

Metabolism and toxicity of anacrotine, a pyrrolizidine alkaloid, in rats

The effects of anacrotine, a pyrrolizidine alkaloid (PA) which has the structure of senecionine with an additional 6-hydroxy group, have been investigated in weanling male rats. When anacrotine was given i.p. (100 mg/kg), pyrrolic metabolites reached a peak level in the liver during the first 0.5 h, then fell rapidly to a lower level which subsequently declined more slowly. Pyrrolic metabolites accumulated in the lungs during the first hour to a level which then remained relatively steady for at least 4 h. The lung level of pyrrolic metabolites after 2 h was about 39% of the liver level, compared with 16% in rats given senecionine. Anacrotine caused acute centrilobular necrosis and congestion of the liver when 125 mg/kg or more was given i.p., but oral doses (up to 180 mg/kg) caused relatively little liver necrosis. Enlarged hepatocytes developed during ensuing weeks, but these were moderate compared with the bizarre giant cells often associated with pyrrolizidine intoxication. In contrast, anacrotine produced much more severe lung damage than most other pyrrolizidine alkaloids. The lungs were affected by i.p. or oral doses well below those needed to produce acute liver damage. Pulmonary congestion and oedema, extensive necrosis of the pulmonary endothelium, and thickening of alveolar septae, developed within 2 days after dosing. After single i.p. doses of 60 mg/kg or more progressive consolidation of lung tissue often led to death after 2-5 weeks. Hearts showed myocardial necrosis of the right ventricular wall. Dehydroanacrotine, the putative reactive pyrrolic metabolite of anacrotine, given i.v. to rats, caused dose-related chronic lung and heart damage identical to that produced by anacrotine, but after lower doses (6-27 mg/kg); larger amounts caused acute lung damage. It is suggested that the severe lung damage in animals given anacrotine is due to dehydroanacrotine, formed in the liver. This metabolite is more stable than the pyrrolic derivatives of most other pyrrolizidine alkaloids, and it is thus able to reach the lungs in relatively large amounts.     

Preliminary studies on acute and subacute toxicity of an antidiabetic herbal preparation, Dianex

Dianex, a polyherbal formulation intended to use for diabetic patients, has been screened for toxic effects. For acute toxicity studies, Dianex was administered orally in graded doses of 0.75-10 g/kg to the mice. For subacute toxicity studies, different doses of Dianex (1.0, 1.5 and 2.5 g/kg) were administered orally to the rats once daily for 30 days. Animals were observed for physiological and behavioural responses, mortality, food and water intake and body weight changes. Hematological evaluation was performed weekly. All the animals were sacrificed on 31st day and changes in organ weights and histology were examined. Biochemical studies were done in liver and serum. No mortality was observed up to 10 g/kg of Dianex in acute toxicity study. Daily administration of as high as 2.5 g/kg dose of Dianex did not result in any mortality or changes in gross behaviour, body weight, weight and histology of different organs or serum and liver biochemistry. However, significant increase in RBC count and hemoglobin level was observed in the treated animals at all doses. Other peripheral blood constituents were in the normal range. The dose of Dianex to produce significant antidiabetic activity in mouse, 0.25-0.5 g/kg, is much lower than the doses used in the present study. Therefore such doses may be safe for daily administration without causing any serious side effects.     

Stimulation of nonspecific resistance to infection by a crude cell wall preparation from Mycobacterium phlei

Fox, Alfred E. (Warner-Lambert Research Institute, Morris Plains, N.J.), George L. Evans, Frank J. Turner, Benjamin S. Schwartz, and Ansel Blaustein. Stimulation of nonspecific resistance to infection by a crude cell wall preparation from Myocobacterium phlei. J. Bacteriol. 92:1-5. 1966.-Exposure of large quantities of viable Mycobacterium phlei to attrition in a colloid mill resulted in 90 to 95% disruption of the organisms. Isolation of the crude cell wall preparation was accomplished by centrifugation of the broken cells at 10,000 x g, resuspension of the sediment, and repeated centrifugation at 1,000 x g to remove intact cells. Single oral or parenteral doses of the cell wall preparation increased the resistance of mice and guinea pigs to experimental infection with Salmonella enteritidis, and of mice to Staphylococcus aureus, for prolonged periods after administration. Histological examination of the organs of mice treated orally or intraperitoneally revealed a lymphoid hyperplasia of the spleen and a Kupffer cell proliferation of the liver. The preparation was nontoxic to mice by the oral route at doses up to 5,000 mg/kg, and the intraperitoneal ld(50) was approximately 680 mg/kg.     

Study of general toxic and organotropic properties of clindamycin in long-term experiments]

The action of clindamycin monohydrate on the general state and weight rise, liver and kidney functions, peripheral blood count and pathomorphological state of the viscera was studied on rats in chronic experiments. Clindamycin was administered to laboratory animals orally in doses of 50, 100, 150 and 300 mg/kg. It was shown that some adverse reactions to the drug and in particular disorders in blood coagulation and morphological changes in the intestine did not depend on its dose and were due to duration of the drug use and probable development of dysbacteriosis. At the same time the disorders in the liver and kidney functions though transitory did depend, to a greater extent, on the dose and were evident after the antibiotic overdosage.     

Chronic glucose-lowering effects of rosiglitazone and bis(ethylmaltolato)oxovanadium(IV) in ZDF rats

The aim of this study was to determine if there was a synergistic or additive effect of a thiazolidinedione derivative (rosiglitazone (ROS)) and a vanadium compound (bis(ethylmaltolato)oxovanadium(IV) (BEOV)) on plasma glucose and insulin levels following chronic oral administration to Zucker diabetic fatty (ZDF) rats. Whole-blood vanadium levels were determined at time 0 and at days 1, 6, and 18. The doses of BEOV (0.1 mmol/kg) and ROS (2.8 micromol/kg) were selected to produce a glucose-lowering effect in 30% (ED30) of animals. Both drugs were administered daily by oral gavage as suspensions in 1% carboxymethylcellulose (CMC) in a volume of 2.5 mL/kg. The total volume administered to all rats was 5 mL/(kg.day). The combination of BEOV and ROS was effective in lowering plasma glucose levels to <9 mmol/L in 60% of fatty animals as compared with 30% for BEOV and 10% for ROS alone. The age-dependent decrease in plasma insulin levels associated with beta-cell failure in the ZDF rats did not occur in the BEOV-treated fatty groups. There was no effect of any treatment on body weight; however, there was a significant reduction in both food and fluid intake in fatty groups treated with BEOV. There were no overt signs of toxicity and no mortality in this study. Both BEOV and ROS were effective in lowering plasma glucose levels, as stated above, and there was at least an additive effect when BEOV and ROS were used in combination.     

Toxicogenomic analysis of gene expression changes in rat liver after a 28-day oral benzene exposure

Benzene is an industrial chemical, component of automobile exhaust and cigarette smoke. After hepatic bioactivation benzene induces bone marrow, blood and hepatic toxicity. Using a toxicogenomics approach this study analysed the effects of benzene at three dose levels on gene expression in the liver after 28 daily doses. NMR based metabolomics was used to assess benzene exposure by identification of characteristic benzene metabolite profiles in urine. The 28-day oral exposure to 200 and 800 mg/kg/day but not 10 mg/kg/day benzene-induced hematotoxicity in male Fisher rats. Additionally these upper dose levels slightly reduced body weight and increased relative liver weights. Changes in hepatic gene expression were identified with oligonucleotide microarrays at all dose levels including the 10 mg/kg/day dose level where no toxicity was detected by other methods. The benzene-induced gene expression changes were related to pathways of biotransformation, glutathione synthesis, fatty acid and cholesterol metabolism and others. Some of the effects on gene expression observed here have previously been observed after induction of acute hepatic necrosis with bromobenzene and acetaminophen. In conclusion, changes in hepatic gene expression were found after treatment with benzene both at the toxic and non-toxic doses. The results from this study show that toxicogenomics identified hepatic effects of benzene exposure possibly related to toxicity. The findings aid to interpret the relevance of hepatic gene expression changes in response to exposure to xenobiotics. In addition, the results have the potential to inform on the mechanisms of response to benzene exposure.     

Carvacrol partially reverses symptoms of diabetes in STZ-induced diabetic rats

Little is known about the protective effects of carvacrol on the symptoms of streptozotocin induced diabetes in rats. Hence, this present study was designed to evaluate the protective effect of the strong antioxidant, carvacrol, on the symptoms of streptozotocin induced diabetes in rats. Carvacrol at the doses of 25 and 50 mg/kg body weight were orally administered to diabetic rats for a period of 7 days after the onset of diabetes. Food-water intake and body weight changes were daily recorded. Biochemical parameters such as serum glucose, insulin, total cholesterol, alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase were measured. Although treatment of diabetic rats with oral administration of carvacrol resulted in a slight reduction in serum glucose level and significant reduction in serum total cholesterol, alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase in comparison with diabetic control rats, there were no significant differences in serum insulin levels, food-water intake values and body weight changes. Despite the inadequacy of carvacrol on diabetes treatments, it was determined to have at least a partially protective role on liver enzymes.     

Metformin-like effects of Quei Fu Di Huang Wan, a Chinese herbal mixture, on streptozotocin-induced diabetic rat.

Effect on plasma glucose concentration of Quei Fu Di Huang Wan (Quei Fu DHW), the herbal mixture widely used to treat diabetic disorder in Chinese traditional medicine, was investigated in diabetic rats deficient in insulin. Changes of plasma glucose in streptozotocin-induced diabetic rats (STZ-diabetic rats) receiving repeated oral administration of Quei Fu DHW were determined. Also, the mRNA level (by Northern blotting) and protein level (by Western blotting) of phosphoenolpyruvate carboxykinase (PEPCK) in liver from STZ-diabetic rats were measured to compare differences between groups receiving repeated oral administration of Quei Fu DHW, metformin, and two active herbs (Zou Guei or Fuzei) at effective dosages. In STZ-diabetic rats, acute oral administration of Quei Fu DHW decreased the plasma glucose level significantly in a dose-dependent manner from 5 mg/kg to 26.0 mg/kg. Similar treatment with Quei Fu DHW also brought on a plasma glucose-lowering effect in normal rats, although the effectiveness was not as significant as in STZ-diabetic rats. Repeated oral treatment of Quei Fu DHW at 26 mg/kg every 8 h, three times daily for 3 days, produced a plasma glucose-lowering activity similar to that of metformin-treatment in STZ-diabetic rats. Oral administration of Zou Guei (Cinnamomi Cortex) or Fuzei (Aconiti Tuber), the individual constituent of Quei Fu DHW, at the dose of 50 mg/kg into STZ-diabetic rats for 3 days normalized hyperglycemia. Similar to the repeated treatment with Quei Fu DHW, Fuzei at the effective dose reversed the elevated mRNA and protein levels of PEPCK in liver from STZ-diabetic rats. This is consistent with findings that metformin restored the increased gene expression of PEPCK in liver from STZ-diabetic rats. However, the gene expression of PEPCK in STZ-diabetic rats was not influenced by similar treatment with Zou Guei. The present study found that oral administration of Quei Fu DHW could decrease hepatic gluconeogenesis in a way similar to metformin in lowering plasma glucose in diabetic rats lacking insulin. Thus, this preparation may be a helpful adjuvant for the treatment of diabetic disorders in clinical practice.     

Activity of quinfamide against natural infections of Entamoeba criceti in hamsters: a new potent agent for intestinal amoebiasis

A novel tetrahydroquinolinyl ester, quinfamide, administered orally in multiple doses for 3 days had an ED50 of 0.25 mg/kg/day (total dose 0.75 mg/kg) for eradicating Entamoeba criceti in hamsters in several tests. It was significantly more active by direct comparison than 3 commercially available amoebicides and at least as active as 2 other esters of the parent compound, 1-(dichloroacety)-1,2,3,4-tetrahydro-6-quinolinol. After administration of a single dose, ED50 calculations for quinfamide averaged 0.9 mg/kg. Quinfamide was considerably more active than the other tetrahydroquinolinols, diloxanide furoate and teclozan, and it was approximately 1.5 times more active than etofamide; a statistical significance between the latter 2 drugs could be demonstrated in one of 4 tests. Administered prophylactically, quinfamide was shown to protect hamsters from re-infection with E. criceti. It also inhibited propagation of E. histolytica in vitro at a concentration of 20 microgram/ml. No adverse effects were noted in rodents after a single dose as high as 10 g/kg. Daily administration to monkeys of doses up to 500 mg/kg for as long as 37 days produced no pharmacological aberrations during or after medication; haematological studies and urine analyses were normal and no gross or microscopical tissue changes attributable to quinfamide were observed. No toxicity was revealed following acute (2 g/kg) and chronic (500 mg/kg/day x 31 days) administration of the drug to dogs and rats, respectively.     

鳖甲育肝颗粒对乙醇性肝纤维化大鼠的影响*

目的:探讨鳖甲育肝颗粒对乙醇性肝纤维化大鼠的防治作用。方法:将SD大鼠随机分为空白对照组、模型对照组、鳖甲育肝颗粒对照组、秋水仙碱组、鳖甲育肝颗粒低剂量组和鳖甲育肝颗粒高剂量组(n=8),采用梯度乙醇灌胃法复制肝纤维化动物模型,即除了空白对照组及鳖甲育肝颗粒对照组灌胃等量纯净水外,其余各组大鼠第1～4周灌胃5 g/(kg·d)乙醇,第5～8周灌胃7 g/(kg·d)乙醇,第9～12周灌胃9 g/(kg·d)乙醇,第13～24周灌胃9.5 g/(kg·d)乙醇,其中乙醇剂量计算采用下列公式:乙醇剂量(g) = 无水乙醇体积(ml)×预配乙醇浓度(%)×0.8(g/ml),同时每天灌胃相应的药物:鳖甲育肝颗粒对照组灌胃鳖甲育肝颗粒5.55 g/kg、秋水仙碱组灌胃秋水仙碱0.1 mg/kg、鳖甲育肝颗粒低剂量组灌胃鳖甲育肝颗粒1.85 g/kg、鳖甲育肝颗粒高剂量组灌胃鳖甲育肝颗粒5.55 g/kg,空白对照组及模型对照组灌胃等量纯净水。实验第169日观测鳖甲育肝颗粒对大鼠肝脏脏器宏观变化、肝组织含水量及其纤维化病理变化、肝组织羟脯氨酸(Hyp)含量及α-平滑肌肌动蛋白(α-SMA)、CREB表达水平的影响。结果:1.85、5.55 g/kg鳖甲育肝颗粒能明显改善乙醇性肝纤维化大鼠肝脏脏器宏观变化及肝组织纤维化病理变化,降低肝组织含水量及Hyp的含量,下调α-SMA、CREB表达水平。结论:鳖甲育肝颗粒具有明显的抑制乙醇性肝纤维化的作用,而下调CREB是其抗肝纤维化的作用机制之一。     

Histological changes in the liver of fetuses of alcohol-treated pregnant rats

In this study, immunolocalization of tenascin (TN), type IV collagen and histopathological changes in the liver of fetuses of pregnant Wistar albino rats treated with two doses of alcohol (1 and 5 g kg(-1) day(-1)) were determined. The samples of liver obtained from fetuses of rats on day 21 of gestation were evaluated morphologically and fixed for histology and immunohistochemistry. The sections stained with H&E and peroxidase-antiperoxidase (PAP) method for TN and type IV collagen were evaluated and immunohistochemical staining results were examined by the intensity of labelling. Statistical evaluation of data showed that there were no differences in liver weights between the control and calorie control groups; but some differences in relative liver weight between the control and alcohol treatment groups were determined. The changes in the liver histology such as degeneration of the cytoplasm of hepatocytes and increases in the number of megakaryocytes were seen in the fetuses of groups receiving alcohol during pregnancy. Increases in the immunolocalization of TN and type IV collagen in the liver of fetuses of alcohol-receiving rats were also found.     

Lack of first-pass metabolism of ethanol at blood concentrations in the social drinking range

Previously published data are displayed in a new manner and show that there is complete systemic availability of oral doses of 23-47 g of ethanol (0.35-0.75 g/kg or 30-60 ml of 95% ethanol) in man when administered in the fasting state relative to an intravenous infusion of the same doses administered over a 2-hr period. A previous report by other authors that oral ethanol (0.15 g/kg) in man had a mean systemic availability of only 29% is explained by the fact that the subjects were fed one hour prior to administration of the alcohol and that the intravenous dose was infused over only a 20 minute period.     

Acute and sub-acute toxicity of an insect pheromone, N-heneicosane and combination with insect growth regulator, diflubenzuron, for establishing no observed adverse effect level (NOAEL)

Aedes aegypti mosquito is one of the most notorious vectors of dangerous diseases like dengue hemorrhagic fever and chikangunya. One method of control of the vectors is by the use of semiochemicals or pheromones. The pheromone n-heneicosane (C21) has been proved to be effective in attracting the female Aedes aegypti to lay eggs in the treated water and the growth of the larva is controlled by insect growth regulator diflubenzuron (DB). This study was planned to assess the safety of C21 alone and the combination with DB. Acute toxicity tests were carried out using two doses, viz., 1600 and 3200 mg/kg and two routes of exposure oral and intra-peritoneal. Dermal toxicity test was carried out in both male and female rats at the dose of 3200 mg/kg. Primary skin irritation test was carried out in rabbits. Sub-acute (90 days) dermal toxicity studies in male and female rats at the dose of 1 and 2 mg/kg via the per-cutaneous route were also studied. Sub-acute (90 days) toxicity test through the oral route was carried out, at doses 125, 250 and 500 mg/kg in male and female rats. The calculated LD50 by ip route and dermal route was more than 5 g/kg in mouse and rats of both the sexes. In the primary skin irritation test no significant changes were noted. In the sub-acute toxicity studies even 500 mg/kg dose was not able to produce toxic response in rats when they were dosed daily for 90 days. The established no observed adverse effect level (NOAEL) was more than 500 mg/kg.     

Effect of catamine AB on the generative function and chromosome apparatus of the bone marrow cells in white rats

In a chronic experiment (6 months) performed on non-inbred white rats effect of cationic superficially active substance catamin AB on the structure and function of male and female gonads, state of the offspring and on the chromosome apparatus of the bone marrow cells has been studied. The preparation is intragastrically injected in doses 10, 1, 0.1 mg/kg. Catamin AB in the dose of 10 mg/kg produces an essential decrease in the specific mass of the testes, reduce in the spermatogenic index, increase in the canaliculi number with exfoliated epithelium, lowered mobility and diminished amount of alive spermatozoa. In the ovary amount of mature follicles becomes less and the number of atresic corpuscles and atresing follicles rises; plethora of the medullary substance occurs in the organ with signs of stasis in the venous bed. In the dose 1 mg/kg catamin AB results in less pronounced changes in the testes and does not produce any pathological disturbances in the ovaries. The preparation does not influence on mating in the test animals, but in the dose 10 mg/kg results in a decreasing fertility because of pre- and postimplantational death of embryos. The changes mentioned are connected with a total toxical effect of the preparation. Catamin AB does not possess any mutagenic effect in the doses tested.     

The absorption and metabolism in rats of small oral doses of dimethylnitrosamine. Implication for the possible hazard of dimethylnitrosamine in human food.

1. Groups of rats were given one dose of the carcinogen dimethylnitrosamine by gastric intubation. The dose was varied between 10mg/kg body wt. and 1 microgram/kg body wt. 2. The dose was rapidly absorbed. 3. The methylation of liver DNA resulting from the administration of this carcinogen was proportional to dose. This suggests that small doses are absorbed from the gut with no more loss than large doses. 4. As the dose was decreased there was a disproportionately greater decrease in the alkylation of kidney DNA, and when the dose was less than 40 microgram/kg body wt. the methylation of kidney DNA was no longer detectable. This possibly explains why small amounts of dimethylnitrosamine in the diet do not induce kidney tumours. 5. Comparison of the relative alkylation of liver DNA and kidney DNA resulting from an oral and from an intravenous dose of dimethylnitrosamine suggest that small amounts of dimethylnitrosamine absorbed into the portal blood from the gut are completely metabolized by the liver and do not enter the general circulation. 6. The implications of these results for the possible hazard of dimethylnitrosamine in human food is discussed.