Elevation of micronuclei frequency in mouse bone marrow treated with various doses of teniposide (VM-26)

The effect of various doses (0-10 mg/kg body wt.) of teniposide (VM-26) was studied on the induction of micronuclei at 12, 24 and 36 h post-treatment. The frequency of micronuclei (MPCE and MNCE) increased in a dose-dependent manner up to a dose of 0.3125 mg/kg VM-26, where a peak frequency of micronuclei was observed. A further increase in the drug dose resulted in the reduction in micronuclei frequency in comparison with 0.3125 mg/kg drug dose reaching a nadir at 10 mg/kg. However, it was significantly higher than DDW (double distilled water) treated controls. The pattern of micronuclei induction was similar for all the post-treatment time periods. The frequency of micronuclei also increased with scoring time and the highest frequency of micronuclei was observed at 24 h post-treatment, which declined thereafter without restoration to DDW treated control level. Conversely, the PCE/NCE ratio registered a dose-dependent decline after treatment of mice with various doses of VM-26. A peak decline was observed at a dose of 0.3125 mg/kg, thereafter the decline became consistently less resulting in an elevation in the PCE/NCE ratio in comparison with 0.3125 mg/kg VM-26.     

In vivo micronucleus assay and GST activity in assessing genotoxicity of plumbagin in Swiss albino mice

Information available on the mutagenicity of a large number of indigenous drugs commonly employed in the Siddha and Ayurveda systems of medicine is scanty. In this context, the current investigation on plumbagin, 5-hydroxy-2methyl-1,4-napthoquinone, an active principle in the roots of Plumbago zeylanica used in Siddha and Ayurveda for various ailments, was carried out; 16 mg/kg b.w. (LD(50)) was fixed as the maximum dose. Subsequent dose levels were fixed as 50% and 25% of LD(50) amounting to 8 mg and 4 mg/kg b.w., respectively, and given orally for 5 consecutive days in 1% Carboxyl Methyl Cellulose (CMC) to Swiss albino mice weighing 25-30 g. The micronucleus assay was done in mouse bone marrow. Plumbagin was found to induce micronuclei at all the doses studied (4 mg/kg, 8 mg/kg, 16 mg/kg b.w.), and it proves to be toxic to bone marrow cells of Swiss albino mice. Animal treated with cyclophosphamide (40 mg/kg b.w.) served as positive control. In addition, glutathione S-transferase (GST) activity was observed in control, plumbagin (4 mg, 8 mg, 16 mg/kg b.w., respectively), and genotoxin-treated experimental group of animals. No significant change in GST activity was observed with plumbagin dose of 4 mg/kg b.w., whereas GST activity was significantly inhibited by higher doses of plumbagin (8 mg and 16 mg/kg b.w.) and cyclophosphamide.     

In Vivo Micronucleus Assay and GST Activity in Assessing Genotoxicity of Plumbagin in Swiss Albino Mice

Information available on the mutagenicity of a large number of indigenous drugs commonly employed in the Siddha and Ayurveda systems of medicine is scanty. In this context, the current investigation on plumbagin, 5-hydroxy-2methyl-1,4-napthoquinone, an active principle in the roots of Plumbago zeylanica used in Siddha and Ayurveda for various ailments, was carried out; 16 mg/kg b.w. (LD₅₀) was fixed as the maximum dose. Subsequent dose levels were fixed as 50% and 25% of LD₅₀ amounting to 8 mg and 4 mg/kg b.w., respectively, and given orally for 5 consecutive days in 1% Carboxyl Methyl Cellulose (CMC) to Swiss albino mice weighing 25–30 g. The micronucleus assay was done in mouse bone marrow. Plumbagin was found to induce micronuclei at all the doses studied (4 mg/kg, 8 mg/kg, 16 mg/kg b.w.), and it proves to be toxic to bone marrow cells of Swiss albino mice. Animal treated with cyclophosphamide (40 mg/kg b.w.) served as positive control. In addition, glutathione S-transferase (GST) activity was observed in control, plumbagin (4 mg, 8 mg, 16 mg/kg b.w., respectively), and genotoxin-treated experimental group of animals. No significant change in GST activity was observed with plumbagin dose of 4 mg/kg b.w., whereas GST activity was significantly inhibited by higher doses of plumbagin (8 mg and 16 mg/kg b.w.) and cyclophosphamide.     

Chronopharmacokinetics of indomethacin in rats

In order to establish the origin of the circadian variations in the kinetics of indomethacin (Indocid) observed in humans, a chronopharmacokinetic study was developed in rats. In a first experiment, 3 groups of 24 h fasted rats each received a single i.v. dose of 0.25 or 0.5 or 1 mg/kg b.w. of indomethacin, respectively, at 8 h. Thus it could be demonstrated that the pharmacokinetics of indomethacin were linear in the dose range studied and obeyed a two-compartment model. In a second experiment, 3 other groups of rats from same strain received a single i.v. dose of 0.5 mg/kg b.w. of indomethacin at 2 h, 14 h and 20 h, respectively. In the 4 groups of rats having received 0.5 mg/kg b.w. of indomethacin, it was observed that only the pharmacokinetic parameters which reflected the distribution process exhibited significant circadian variations. When the animals were dosed at 2 h (physiological rest time for rats) the initial plasma concentration (Co = 4.2 +/- 0.08 micrograms/ml) and the area under the curve (AUC = 13.6 +/- 0.5 h micrograms/ml) was significantly lower while the distribution volume (Vd/b.w. = 120 +/- 2 ml/kg) and the total metabolic clearance (ClT/b.w. = 25 +/- 1.1 ml/h/kg) were higher than those observed in rats dosed at 20 h (period of activity). The apparent elimination half-life was not significantly altered by the time of administration. These results are in good agreement with those that we have previously reported in humans orally dosed with indomethacin, and suggest that the mechanisms of the circadian changes of the pharmacokinetics of indomethacin are mainly related to alterations in the drug distribution.     

Stimulation of the acid secretion of the stomach in rats with and without antrectomy in the perfusion test with betazole]

In the perfusion test of the stomach of rats the stimulation of acid secretion by betazol (Histalog) after one or repeated injections was studied. The experiments yielded the following results: 1. The i.v. injection of 20 mg/kg b.w. betazol was followed by a maximun acid secretion. 2. Another infusion two hours later intensified this effect. The same acid secretion was seen after a small initial dose (5 mg/kg b.w.) half an hour before the infusion of betazol. 3. The i.v. infusion of 30 mg/kg b.w. betazol showed in the intact rat stomach a smaller acid dsecretion response than did the dose of 20 mg/kg b.w. In comparison there was a significant higher stimulation with 30 mg/kg b.w. betzaol in the rat after a distal gastrectomy (antrectomy). 4. One s.c. injection of 50 mg/kg b.w. betazol showed a significant acid response of the parietal cells with a duration of at least 7 h on a percentage comparison.     

The in vivo genotoxic effects of carvacrol and thymol in rat bone marrow cells

The aim of this study was to investigate the in vivo genotoxic effects of carvacrol and thymol in bone marrow cells of rats. In the present study, both carvacrol (10, 30, 50, and 70 mg/kg b.w.) and thymol (40, 60, 80, and 100 mg/kg b.w.) significantly induced the structural and total chromosome abnormalities (CA) for all treatment periods (6, 12, and 24 h) when compared with control in bone marrow cells of rats intraperitonally administered. Both carvacrol and thymol showed similar effects with the positive control urethane on induction of the percentage of structural and total CA at the highest concentrations except the effects of carvacrol for 6 h treatment (70 mg/kg b.w. and 100 mg/kg b.w., respectively). In addition, carvacrol induced the numerical CA at all concentrations when compared to control and at two highest concentrations (50 and 70 mg/kg b.w.) when compared to solvent control. Thymol also induced the numerical CA especially at the highest concentration (100 mg/kg b.w.) for all treatment periods. It was shown that there was a dose-dependent effect on induction of structural, numerical and total CA for both carvacrol and thymol. Carvacrol and thymol decreased the mitotic index (MI) in all the concentrations and treatment times when compared with control. Carvacrol showed the similar effects with EC on decreasing the MI at 70 mg/kg b.w. for 6 h, at 30 and 50 mg/kg b.w. for 12 h and at all concentrations for 24 h treatment periods. Thymol also showed a similar effect with urethane (ethyl carbamate, EC) on decreasing the MI at 60, 80, and 100 mg/kg b.w. for 6 h and at all concentrations for 24 h treatment periods. Test substances decreased the MI in a dose-dependent manner.     

Chemoprotective effects of hesperidin against genotoxicity induced by cyclophosphamide in mice bone marrow cells

The preventive effect of hesperidin as a flavonoid was investigated in mouse bone marrow cells against genotoxicty induced by cyclophosphamide. Mice were orally (gavages) pretreated with solutions of hesperidin at four different doses (50, 100, 200, and 400 mg/kg b.w.) for five consecutive days. Mice were injected intraperitoneally on the fifth day with cyclophosphamide (50 mg/kg b.w.) and killed after 24 h for the evaluation of micronucleated polychromatic erythrocytes (MnPCEs) and the ratio of PCE/(PCE+NCE) (polychromatic erythrocyte/ polychromatic erythrocyte + normochromatic erythrocyte). Three last doses of hesperidin significantly reduced frequency of MnPCEs induced by cyclophosphamide (p<0.0001). Hesperdin at dose 200 mg/kg b.w. reduced MnPCEs 2.37 time and also completely normalized PCE/ (PCE+NCE) ratio. Histological examination of bone marrow showed that hesperidin affected on proliferation and hyper cellularity of immature myeloid elements in bone marrow that reduced by cyclophsopahmide. It is obvious that hesperidin, may with antioxidative activity, reduced the oxidative stress and genotoxicity induced by cyclophosphamide in mouse bone marrow cells.     

Locoregional application of 5-fluorouracil to the liver: alteration of pharmacokinetics and bone marrow toxicity in rats with thioacetamide-induced cirrhosis

Pharmacokinetics and toxicity of 5-fluorouracil (5-FU) applied intra-arterially into the liver were studied in control and cirrhotic rats. Cirrhosis was induced by administering thioacetamide (4.5 mg/rat X day) over 6 months. 5-FU was administered into the hepatic artery at 30 mg/kg b.w. by bolus injection followed by infusion of 0.63 mg/kg X min for 40 min. Pharmacokinetics of 5-FU in plasma was studied by HPLC analysis. 5-FU induced toxicity was examined in a second group of control and cirrhotic rats at 48 and 168 hours after treatment with 5-FU (31.4 mg/kg b.w.) infused into the liver artery for 1 h. Analysis of toxicity was carried out by determining liver enzymes in plasma, bone marrow cellularity and colony forming units in vitro (CFU-C) and in vivo (CFU-S). The results indicate that during the period investigated (85 min) 5-FU was not eliminated from the plasma of cirrhotic rats in contrast to controls. The constant level of 5-FU in the plasma of cirrhotic rats induced a considerably higher myelosuppression in these animals, than the short-lived 5-FU peak in controls.     

Assessment of acetamiprid-induced genotoxic effects in bone marrow cells of Swiss albino male mice

Acetamiprid (ACE), a neonicotinoid insecticide, is widely used in agriculture either alone or in combination with other insecticides. A combined approach employing micronucleus test (MNT) and chromosomal aberrations (CA) assay was utilized to assess the genotoxic effects of ACE in bone marrow of Swiss albino male mice. Acetamiprid was administered i.p. daily at 4.6 and 2.3?mg/kg/day along with 3% gum acacia as negative control for 60 and 90?days and cyclophosphamide (50?mg/kg b.wt.) as positive control. ACE treatment resulted in a dose-dependent increase in the frequencies of micronuclei per cell and chromosomal aberrations in bone marrow cells. The increased micronuclei formation in total erythrocyte cells (immature PCEs and mature NCEs) was observed only at higher dose level (4.6?mg/kg b.wt.) administered for 90?days. The test also indicated the cytotoxic effect of higher dose level of pesticide by PCE/NCE ratio. The number of chromosomal aberrations were increased in the pesticide treated group compared to the negative control group, although significant increase was observed only in the group exposed to higher dose level of pesticide for both 60 and 90?days. Thus, daily exposure of ACE at a dose level of 4.6?mg/kg body weight for 60 and 90?days caused genotoxic and cytotoxic effects on the somatic cells of Swiss albino male mice.     

Modulatory effects of gentisic acid against genotoxicity and hepatotoxicity induced by cyclophosphamide in Swiss albino mice

Objectives This study evaluated the protective effects of gentisic acid (GA) against genotoxicity and hepatotoxicity induced by cyclophosphamide (CP) in Swiss albino mice. Methods Mice were pretreated with GA orally at doses of 50 and 100 mg/kg for 14 consecutive days before the administration of a single intraperitoneal dose of 50 mg/kg CP. The ameliorative effect of GA on genotoxicity was studied using the in‐vivo bone marrow micronuclei induction test, DNA integrity and alkaline unwinding assay. The activity of various oxidative stress enzymes were estimated in hepatic tissue. Key findings A single intraperitoneal administration of CP in mice increased the malondialdehyde level, depleted the glutathione content and antioxidant enzyme activity (glutathione peroxidase, glutathione reductase, catalase and quinone reductase), and induced DNA strand breaks and micronuclei induction. Oral pretreatment with GA at both doses caused a significant reduction in malondialdehyde and glutathione levels, restoration of antioxidant enzyme activity, reduction in micronuclei formation and DNA fragmentation. Serum toxicity marker enzymes such as aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase were increased after CP treatment but restored in GA pretreated groups. Conclusion The results support the protective effect of GA against CP induced genotoxicity and hepatotoxicity.     

Increased resistance towards two systemic experimental infections by tetrachlorodecaoxygen anion complex. Possible implications of cellular and humoral immunity

The tetrachlorodecaoxygen anion complex (TCDO, Oxoferin) given intravenously 1 h after intravenous infection of mice with Candida albicans increased the host's resistance gradually in doses up to 3.1 mumol/kg body weight (b.w.). Above this level, the stimulatory effect decreased, turning to an inhibition at a dose of 18.6 mumol/kg b.w. TCDO. Repeated applications of the optimum single dose had no cumulative effect. In experimental infections with the strictly anaerobic Peptostreptococcus intermedius, TCDO ameliorated the course of the infection not only at a dose of 3.1 mumol/kg b.w. but also at a higher dose of 12.4 mumol/kg b.w. TCDO, which in the Candida sepsis model fell into the range of defence inhibition. A single dose of 3.1 mumol/kg b.w. TCDO also revealed to be the optimum dose to increase the humoral immune response evaluated by the number of immunoglobulin (Ig)M and IgG forming spleen cells after sensitization with sheep red blood cells (SRBC). The same results were obtained, regardless of whether TCDO had been given at the time of immunization or thereafter. The higher single dose of 18.6 mumol/kg b.w. TCDO did not show this effect but was not inhibitory either. Cellular immune reactions evaluated by the footpad swelling test and SRBC as antigen were found considerably enhanced whether TCDO was given once or repeatedly at a dose of 3.1 mumol/kg b.w., whereas single doses of 18.6 mumol/kg or repeated doses of 9.3 mumol/kg induced a certain inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effect of hawthorn extract against genotoxicity induced by cyclophosphamide in mouse bone marrow cells

The preventive effect of hawthorn (Crataegus microphylla) fruit extract was investigated in mouse bone marrow cells against genotoxicity induced by cyclophosphamide. Mice were orally (gavages) pretreated with solutions of hawthorn extract which was prepared at five different doses (25, 50, 100, 200 and 400mg/kg b.w.) for seven consecutive days. Mice were injected intraperitoneally on the seventh day with cyclophosphamide (50mg/kg b.w.) and killed after 24h for the evaluation of micronucleated polychromatic erythrocytes (MnPCEs) and the ratio of PCE/(PCE+NCE) (polychromatic erythrocyte/polychromatic erythrocyte+normochromatic erythrocyte). All of five doses of extract significantly reduced MnPCEs induced by cyclophosphamide (P<0.0001). Hawthorn extract at dose 100mg/kg b.w. reduced MnPCEs 2.5 time and also completely normalized PCE/(PCE+NCE) ratio. Hawthorn extract exhibited concentration-dependent antioxidant activity on 1,1-diphenyl-2-picryl hydrazyl free radical. Hawthorn contains high amounts of phenolic compounds; the HPLC analysis showed that it contained chlorogenic acid, epicatechin and hyperoside. It is obvious that hawthorn, particularly flavonoids constituents with antioxidative activity, reduced the oxidative stress and genotoxicity induced by cyclophosphamide in mouse bone marrow cells.     

Protective action of ascorbic acid against mutagenicity of aminopyrine plus nitrite

Mutagenicity of aminopyrine and of aminopyrine plus nitrite was tested by the micronucleus test in bone marrow of mice and by host mediated mutagenicity assay with mice as host animals and S. typhimurium strain G 46. In parallel the possibility of the protective action of ascorbic acid was studied. Aminopyrine at the dose of 90 mg/kg po when administered to mice together with potassium nitrite induced a significant increase in the frequency of micronuclei in polychromatic erythrocytes and proved to be mutagenic for a Salmonella strain. In both systems mutagenicity of the combination of aminopyrine at this dose plus nitrite was abolished completely by ascorbic acid (373 or 622 mg/kg po). Ascorbic acid neither induced a significant increase in the frequency of micronuclei nor was mutagenic for the strain G 46. A formulation of aminopyrine with ascorbic acid is proposed.     

Route-dependent effects of cadmium/cadmium and magnesium acute treatment on parameters of oxidative stress in rat liver

The study was designed to evaluate and compare the effects of single oral (or) and intraperitoneal (i.p.) cadmium (Cd) administration on parameters of oxidative stress in liver of rats. Furthermore, investigation on protective effects of magnesium (Mg) or and i.p. pretreatment on the same parameters was performed. Wistar rats were administrated oral dose of Cd (30 mg Cd/kg b.w.)/Cd+Mg (30 mg Cd/kg b.w., 50 mg Mg/kg b.w.) or i.p. dose of Cd (1.5 mg Cd/kg b.w.)/Cd+Mg (1.5 mg Cd/kg b.w., 3 mg Mg/kg b.w.) and sacrificed after 24 h. In liver homogenates superoxide anion, malondialdehyde, non-protein sulfhydryl groups, total sulfhydryl groups content, and superoxide dismutase activity were determined. Cadmium intoxication caused the increase of superoxide anion and malondialdehyde levels and had negative effect on investigated parameters of antioxidant defense system, except on total sulfhydryl groups. The negative effect was more emphasized after i.p. Cd administration. Oral Mg pretreatment induced more pronounced positive effect than Mg given intraperitoneally that can be attributed, at least partly, to Cd and Mg interactions on the level of GIT. On the basis of the obtained results it can be concluded that both Cd and Cd+Mg effects on parameters of oxidative stress in rats liver are route-dependent.     

Polysaccharides isolated from Ganoderma lucidum occurring in Southern parts of India, protects radiation induced damages both in vitro and in vivo

The in vivo and in vitro radioprotective property of the polysaccharides isolated from Ganoderma lucidum were determined by survival studies, induction of micronucleus in reticulocytes of mice, strand breaks in plasmid pBR322 DNA and inhibition of lipid peroxidation (TBARS assay). Polysaccharides were administered as a single dose after whole body exposure to 10 Gy ⁶⁰Co γ-radiation to Swiss albino mice. At a dose of 500 μg/kg body wt, the polysaccharides were most effective in protecting animals from radiation induced loss of lethality. Administration of 500 μg/kg body wt to animal exposed to 10 Gy gamma radiation resulted in more than 60% survival on the 30th day compared to the dose of 300 mg/kg/body wt administration of amifostine, a clinically used radioprotective drug. The induction of micronuclei was reduced by the administration of polysaccharides. The decrease in micronuclei induction was dose dependent. Thus following 4 Gy exposure the micronuclei in polychromatic erythrocytes (MNCE) was reduced from 28.16 ± 3.049 to 16.0243 ± 2.074 and 6.30 ± 2.422 by polysaccharides at doses of 250 μg/kg body wt and 500 μg/kg body wt, respectively, and to 10.4 ± 2.581 by amifostine at a dose of 300 mg/kg body wt. The results indicate the significant protective effect of Ganoderma polysaccharides against radiation induced damages. The findings thus suggest the potential use of Ganoderma polysaccharides as novel radioprotective agent.     

Pentadecapeptide BPC 157 attenuates disturbances induced by neuroleptics: the effect on catalepsy and gastric ulcers in mice and rats.

A gastric pentadecapeptide, BPC 157, with the amino acid sequence, Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val, MW 1419, known to have a variety of protective effects in gastrointestinal tract and other organs, was recently shown to particularly affect dopamine systems. For instance, it blocks the stereotypy produced acutely by amphetamine in rats, and the development of haloperidol-induced supersensitivity to amphetamine in mice. Consequently, whether pentadecapeptide BPC 157, that by itself has no cataleptogenic effect in normal animals, may attenuate the immediate effects of neuroleptics application, particularly catalepsy, was the focus of the present report. Prominent catalepsy, otherwise consistently seen in the mice treated with haloperidol (0.625, 1.25, 2.5, 5.0 and 10.0 mg/kg b.w., i.p.) and fluphenazine (0.3125, 0.625, 1.25, 2.5 and 5.0 mg/kg b.w., i.p.) after 1.5, 3, 4.5, 6 and 7.5 h following administration, was markedly attenuated when pentadecapeptide BPC 157 (10 microg or 10 ng/kg b.w., i.p.) was coadministered with the neuroleptic. The number of cataleptic mice was markedly lower throughout most of the experimental period. Moreover, on challenge with lower doses of neuroleptics, catalepsy appearance was postponed and the mice, otherwise cataleptic since the earliest period, became cataleptic later, not before 3 or 4.5 h after neuroleptic administration, especially if protected with higher pentadecapeptide dose. Besides catalepsy, coadministration of the pentadecapeptide BPC 157, given in the above mentioned doses, reduced not only catalepsy but somatosensory disorientation (for 7.5 h after administration of a neuroleptic, assessed at intervals of 1.5 h, by a simple scoring system [0-5]) in haloperidol- or fluphenazine-challenged mice as it did in mice treated with sulpiride (20, 40, 80 and 160 mg/kg b.w., i.p.) or with clozapine (25, 50 and 100 mg/kg b.w., i.p.), in which case catalepsy was absent. In other experiments, considering the gastric origin of this pentadecapeptide, the focus was shifted to the evidence that a dose of haloperidol, cataleptogenic due to dopamine receptors blockade, induces gastric ulcers in rats. Coadministration of pentadecapeptide BPC 157 (10 microg, 10 ng, 1.0 ng, 100 pg/kg b.w., i.p.) to rats completely inhibited the lesions otherwise regularly evident 24 h after haloperidol (5.0 mg/kg b.w., i.p.) in control rats (18 of 20 rats had gastric lesions). This activity accompanied the antagonism of the haloperidol catalepsy in rats (assessed at 60-min intervals from I to 5 h after haloperidol), when 10-microg- or 10-ng regimens were given (lower doses could not influence catalepsy). Together, these findings indicate that pentadecapeptide BPC 157 fully interacts with the dopamine system, both centrally and peripherally, or at least, that BPC 157 interferes with some steps involved in catalepsy and/or ulcer formation.     

High-dose clastogenic activity of aniline in the rat bone marrow and its relationship to the carcinogenicity in the spleen of rats

To clarify the question of clastogenicity of aniline in rats two studies were performed: a bone marrow micronucleus test and a bone marrow metaphase test. In the micronucleus test aniline (as aniline hydrochloride) was administered to groups of seven male PVG rats at single oral doses of 0, 300, 400, or 500 mg/kg body weight. Bone marrow was obtained 24 and 48 h after oral treatment. Smears of bone marrow were stained with acridine orange and erythrocytes were examined for the presence of micronuclei. Animals receiving cyclophosphamide (1x7.5 mg/kg) served as positive controls. Clinical signs observed in animals dosed at 300 mg/kg and above included cyanosis, light brown coloured urine and cold to touch. Small, but statistically significant and dose-related increases in the incidence of micronulei over the vehicle control values were observed at the 24-h sampling time only. Cyclophosphamide induced a significant and comparably much higher increase in micronuclei than aniline. In the bone marrow metaphase test aniline (as aniline hydrochloride) was administered to groups of seven male PVG rats at single oral dose levels of 0, 300, 400, or 500 mg/kg body weight. Bone marrow was sampled 18 and 30 h after dosing. A group treated with cyclophosphamide (1x40 mg/kg) served as positive control. A small increase in the percentage of aberrant cells above solvent control values was recorded in one rat at 400 mg/kg and four rats at 500 mg/kg at the 18-h sampling time only. The positive control cyclophosphamide induced a much higher rate of aberrant cells in all animals. Several lines of evidences are presented against a causal relationship between the clastogenic activity in male PVG rats at 400 and 500 mg/kg and the carcinogenicity in the spleen of Fischer 344 rats starting at 30 mg/kg in males. Among these are the dose-response relationship of the tumour incidence, the close correlation between degree of spleen damage and tumour induction, the lack of carcinogenic effects in mice even at higher dose levels, or in rats at dose levels inducing only slight haematotoxicity and spleen toxicity, and the available data on the mode of action of other chemicals inducing spleen tumours.     

Evaluation of cardiovascular effects of caffeine using telemetric monitoring in the conscious rat.

Caffeine (1,3,7 trimethylxanthine) affects the cardiovascular system, with potential toxic effects ranging from a moderate increase in heart rate to more severe cardiac arrhythmias. Telemetry transmitters were implanted in Wistar rats in the peritoneal cavity with a pressure catheter in the aorta and electrodes for electrocardiogram (ECG) recording subcutaneously. After a single oral administration of saline, each rat was administered single oral doses of 5, 15 and 45 mg/kg b.w. of caffeine. Caffeine was found to induce, to various degrees, a dose-dependent early increase in spontaneous physical activity, heart rate, dp/dt and systolic-diastolic blood pressure. No arrhythmias or visual changes were observed in the ECG complex. High doses induced more strong responses and of longer duration. The increase in systolic blood pressure at the median dose remained in the rats until 20 h after administration. However, the highest dose of caffeine (45 mg/kg b.w.) induced a biphasic response, with an early and pronounced increase in body temperature, spontaneous physical activity, systolic and diastolic blood pressure that later decreased, except for the systolic blood pressure. The results show that the dose level for long-lasting signs of intoxication to develop in the rat, in terms of effects on spontaneous physical activity, body temperature and cardiovascular function, was reached after a single oral dose of caffeine at 45 mg/kg b.w.     

Antithrombotic effects of a synthetic inhibitor of activated factor X, JTV-803, in animals

JTV-803, 4-[(2-amidino-1,2,3,4-tetrahydroisoquinolin-7-yloxy)methyl]-1-(4-pyridinyl)piperidine-4-carboxylic acid monomethanesulfonate trihydrate, at > or = 0.1 mg/kg/h inhibited the increase in plasma thrombin-antithrombin III complex in response to continuous infusion of thromboplastin in rats. JTV-803 inhibited thrombus formation in an arteriovenous shunt model by intravenous infusion at > or = 0.3 mg/kg/h and prolonged the occlusion time of photochemically induced arterial thrombus in the middle cerebral artery at >1.5 mg/kg/0.5 h. Activated partial thromboplastin time was prolonged at 10 mg/kg/h. Intravenous administration of JTV-803 prolonged bleeding time at 30 mg/kg/h, a dose 10-100 times higher than the dose that inhibited thrombus formation. Compared with thrombin inhibitor, JTV-803 had less of an effect on the bleeding time. In the arteriovenous shunt model in cynomolgus monkey, JTV-803 prolonged the occlusion time when administered by continuous infusion at 0.3 mg/kg/h or orally at 10 mg/kg. These results suggest that the human factor Xa inhibitor JTV-803 is an orally active anticoagulant that does not affect bleeding time and is useful for the prevention of thrombus.     

Stereochemical pharmacokinetics of the 2-arylpropionic acid non-steroidal antiinflammatory drug flunoxaprofen in rats and in man

Stereospecific serum assays of the non-steroidal antiinflammatory drug flunoxaprofen (S(+)-2-(4-fluorophenyl)-a-methyl-5-benzoxazoleacetic acid, Priaxim) were performed in rats after the oral administration of 10 mg/kg b.w. of the different enantiomeric forms of the drug or of the racemate in order to establish the occurrence and the rate of biotransformation of R(-)-flunoxaprofen to the S(+)-enantiomer, which is the pharmacologically active form. Preliminary observations of the enantiomeric blood levels were also made in man after a single oral dose (100 mg) of R(-)-flunoxaprofen or of the racemate. Blood was withdrawn at different time intervals up to 120 h in rats and up to 48 h in man and serum levels of flunoxaprofen enantiomers were determined by a HPLC method. The results obtained in the rat show that S(+)-flunoxaprofen serum levels following the administration of a single oral dose of flunoxaprofen reach about the same values (between 24 and 30 micrograms/ml at 18 h) whichever form was dosed (i.e. 10 mg/kg b.w. of S(+)- or R(+)-, or 5 mg/kg b.w. of S(+)- as the racemate). On the contrary, R(-)-flunoxaprofen serum concentrations fall to values lower than 5 micrograms/ml either after the administration of 10 mg/kg R(-)- or of 5 mg/kg R(-)- as the racemate; these serum R(-)-flunoxaprofen values are close to those observed after the administration of S(+)-flunoxaprofen which contains 5% R(-)- as an impurity (i.e. 0.5 mg/kg b.w.).(ABSTRACT TRUNCATED AT 250 WORDS)